In view of the problem of unable continuous simulation for large curved surface thin-wall parts milling deformation, Python scripting language is used in pre-processing module of ABAQUS for secondary development. Through the Python script program for the cutting force dynamic loading, the machining deformation prediction problem for large size curved thin-walled parts was solved. The sample simulation and calculation show that the simulation results accord with the actual rule, which proves the machining deformation of large size curved thin-walled parts can be better predicted by using finite element secondary development technique, it provides reference for its application in other fields.