"Then, I went to ticket form in agent panel, , there is no 'Module' field appeared in that form."There is nothing called "ticket form" in the agent panel. And if there was... why would a list (which is not a form) appear in it?"So, what should I do?"Open a ticket? "Is there any step that I miss?"No? You added a new field to Ticket Details. Assuming the visibility of the field is set all future tickets that are opened will have the new field."or do I need to change add anything at backend code?"Generally speaking you should never have change anything in the core files (aka what you call the "backend code")