diff --git a/seahub/settings.py b/seahub/settings.py
index ba97fa5f2a..b73c5ee4f6 100644
--- a/seahub/settings.py
+++ b/seahub/settings.py
@@ -317,6 +317,11 @@ USE_PDFJS = True
 FILE_ENCODING_LIST = ['auto', 'utf-8', 'gbk', 'ISO-8859-1', 'ISO-8859-5']
 FILE_ENCODING_TRY_LIST = ['utf-8', 'gbk']
 HIGHLIGHT_KEYWORD = False # If True, highlight the keywords in the file when the visit is via clicking a link in 'search result' page.
+# Can preview the text file type suffix
+TEXT_PREVIEW_EXT = """ac, am, bat, c, cc, cmake, cpp, cs, css, diff, el, h, html, 
+        htm, java, js, json, less, make, org, php, pl, properties, py, rb,
+        scala, script, sh, sql, txt, text, tex, vi, vim, xhtml, xml, log, csv,
+        groovy, rst, patch, go"""
 
 # Common settings(file extension, storage) for avatar and group avatar.
 AVATAR_FILE_STORAGE = '' # Replace with 'seahub.base.database_storage.DatabaseStorage' if save avatar files to database
@@ -685,4 +690,6 @@ CONSTANCE_CONFIG = {
     'SHARE_LINK_TOKEN_LENGTH': (SHARE_LINK_TOKEN_LENGTH, ''),
     'SHARE_LINK_PASSWORD_MIN_LENGTH': (SHARE_LINK_PASSWORD_MIN_LENGTH,''),
     'ENABLE_TWO_FACTOR_AUTH': (ENABLE_TWO_FACTOR_AUTH,''),
+
+    'TEXT_PREVIEW_EXT': (TEXT_PREVIEW_EXT, ''),
 }
diff --git a/seahub/templates/sysadmin/settings.html b/seahub/templates/sysadmin/settings.html
index d5a20f4751..0877aca83c 100644
--- a/seahub/templates/sysadmin/settings.html
+++ b/seahub/templates/sysadmin/settings.html
@@ -143,6 +143,10 @@
         {% include "snippets/web_settings_form.html" %}
     {% endwith %}
 
+    {% with type="input" setting_display_name="Preview Text ext" setting_name="TEXT_PREVIEW_EXT" setting_val=config_dict.TEXT_PREVIEW_EXT %}
+        {% trans "Each suffix is separated by a comma" as help_tip %}
+        {% include "snippets/web_settings_form.html" %}
+    {% endwith %}
 </div>
 {% endblock %}
 
diff --git a/seahub/utils/__init__.py b/seahub/utils/__init__.py
index 0beaa468a4..82aed1bf21 100644
--- a/seahub/utils/__init__.py
+++ b/seahub/utils/__init__.py
@@ -94,7 +94,6 @@ EMPTY_SHA1 = '0000000000000000000000000000000000000000'
 MAX_INT = 2147483647
 
 PREVIEW_FILEEXT = {
-    TEXT: ('ac', 'am', 'bat', 'c', 'cc', 'cmake', 'cpp', 'cs', 'css', 'diff', 'el', 'h', 'html', 'htm', 'java', 'js', 'json', 'less', 'make', 'org', 'php', 'pl', 'properties', 'py', 'rb', 'scala', 'script', 'sh', 'sql', 'txt', 'text', 'tex', 'vi', 'vim', 'xhtml', 'xml', 'log', 'csv', 'groovy', 'rst', 'patch', 'go'),
     IMAGE: ('gif', 'jpeg', 'jpg', 'png', 'ico', 'bmp'),
     DOCUMENT: ('doc', 'docx', 'ppt', 'pptx', 'odt', 'fodt', 'odp', 'fodp'),
     SPREADSHEET: ('xls', 'xlsx', 'ods', 'fods'),
@@ -334,12 +333,24 @@ def get_user_repos(username, org_id=None):
 
     return (owned_repos, shared_repos, groups_repos, public_repos)
 
+def get_conf_text_ext():
+    """
+    Get the conf of text ext in constance settings, and remove space.
+    """
+    if hasattr(config, 'TEXT_PREVIEW_EXT'):
+        text_ext = getattr(config, 'TEXT_PREVIEW_EXT').split(',')
+        return [x.strip() for x in text_ext]
+    return []
+
 def get_file_type_and_ext(filename):
     """
     Return file type and extension if the file can be previewd online,
     otherwise, return unknown type.
     """
     fileExt = os.path.splitext(filename)[1][1:].lower()
+    if fileExt in get_conf_text_ext():
+        return (TEXT, fileExt)
+
     filetype = FILEEXT_TYPE_MAP.get(fileExt)
     if filetype:
         return (filetype, fileExt)
diff --git a/seahub/views/file.py b/seahub/views/file.py
index ddc394a14b..703b51d717 100644
--- a/seahub/views/file.py
+++ b/seahub/views/file.py
@@ -34,6 +34,7 @@ from django.utils.translation import ugettext as _
 from django.views.decorators.http import require_POST
 from django.template.defaultfilters import filesizeformat
 from django.views.decorators.csrf import csrf_exempt
+from constance import config
 
 from seaserv import seafile_api
 from seaserv import get_repo, send_message, get_commits, \
@@ -55,7 +56,7 @@ from seahub.utils import render_error, is_org_context, \
     mkstemp, EMPTY_SHA1, HtmlDiff, gen_inner_file_get_url, \
     user_traffic_over_limit, get_file_audit_events_by_path, \
     generate_file_audit_event_type, FILE_AUDIT_ENABLED, gen_token, \
-    get_site_scheme_and_netloc
+    get_site_scheme_and_netloc,get_conf_text_ext
 from seahub.utils.ip import get_remote_ip
 from seahub.utils.timeutils import utc_to_local
 from seahub.utils.file_types import (IMAGE, PDF, DOCUMENT, SPREADSHEET, AUDIO,
@@ -328,7 +329,7 @@ def can_preview_file(file_name, file_size, repo=None):
     if repo and repo.encrypted and (file_type in (DOCUMENT, SPREADSHEET, PDF)):
         return (False, _(u'The library is encrypted, can not open file online.'))
 
-    if file_ext in FILEEXT_TYPE_MAP:  # check file extension
+    if file_ext in FILEEXT_TYPE_MAP or file_ext in get_conf_text_ext():  # check file extension
         exceeds_limit, err_msg = file_size_exceeds_preview_limit(file_size,
                                                                  file_type)
         if exceeds_limit:
diff --git a/seahub/views/sysadmin.py b/seahub/views/sysadmin.py
index fd36711d1b..437c2403ab 100644
--- a/seahub/views/sysadmin.py
+++ b/seahub/views/sysadmin.py
@@ -1945,7 +1945,7 @@ def sys_settings(request):
     if HAS_TWO_FACTOR_AUTH:
         DIGIT_WEB_SETTINGS.append('ENABLE_TWO_FACTOR_AUTH')
 
-    STRING_WEB_SETTINGS = ('SERVICE_URL', 'FILE_SERVER_ROOT',)
+    STRING_WEB_SETTINGS = ('SERVICE_URL', 'FILE_SERVER_ROOT', 'TEXT_PREVIEW_EXT')
 
     if request.is_ajax() and request.method == "POST":
         content_type = 'application/json; charset=utf-8'
diff --git a/tests/seahub/views/file/test_constance_text_conf.py b/tests/seahub/views/file/test_constance_text_conf.py
new file mode 100644
index 0000000000..2daec87252
--- /dev/null
+++ b/tests/seahub/views/file/test_constance_text_conf.py
@@ -0,0 +1,32 @@
+from mock import patch
+from django.core.urlresolvers import reverse
+import requests
+
+from constance import config
+
+from seahub.test_utils import BaseTestCase
+
+import datetime
+
+class DefaultText(BaseTestCase):
+    def setUp(self):
+        self.login_as(self.user)
+        self.text = self.create_file(repo_id=self.repo.id,
+                                    parent_dir='/',
+                                    filename='test.az',
+                                    username=self.user.username)
+
+    def test_can_useful(self):
+        self.clear_cache()
+        setattr(config, 'TEXT_PREVIEW_EXT', '')
+        resp = self.client.get(reverse('view_lib_file', args=[
+            self.repo.id,
+            self.text
+            ]))
+        assert resp.context['err'] == 'invalid extension'
+        setattr(config, 'TEXT_PREVIEW_EXT', 'az')
+        resp = self.client.get(reverse('view_lib_file', args=[
+            self.repo.id,
+            self.text
+            ]))
+        assert resp.context['err'] == ''