For the other's answer in Stack Overflow ,I get the correct skill to operate firefox bookmarks. Firefox online bookmarks are stored in the sqlite which named "places.sqlite" as a backup file. In my computer,It is under "C:\Users\xx\AppData\Roaming\Mozilla\Firefox\Profiles\gyhdax0e.default",xx is represented your windows current username,and the latest folder(gyhdax0e.default) will be another name in your computer(such as abcdef.default).
And then you could operate table "moz_places" and "moz_bookmarks" for your function.But please keep signing in.
Sorry ,I forgot the original url.