Thanks for your reply. I can edit the translation now. But I find that the links in article don't add language prefix (es, fr), when click the link, it goes to not translated url, but shows the translation.
Now it's fine. Some tips:
1.If you installed sh404sef, disable "Activate SEO Management" (from Yes to No)
2. Carefull change the plugin order, gtranslate plugin must be in front of cache plugin.
3. The order of plugin should be joomla SEF, gtranslate, sh404sef - System plugin.
One more question:
After I visit the translated url (example: w ww.domain.com/es/, when I go to main url (example: w ww.domain.com), it shows the spanish translation.