Thanks for your reply.
Is there any workaround to load existing formula into dragmath?
To achive this, if we need to change current format LaTex to other format, it is ok, we can change format.
I note that there is save and load express from file feature in dragmath,
Is it possible to call "Save Expression to file" function to save the expression to hidden html field instead of .drgm file?
Then saved expression will load in dragmath from this hidden field to allow the user to edit the expression later.