The invention relates to an assembly welding process method for an aluminum structure ceiling of a driver cab of a motor train unit. The assembly welding process method is characterized in that (1) at the premise of not changing the integral structure of the original structure, ceiling modules are separated, the structure of the original driver cab is re-divided, one part of structure is separated from a left side wall structure and a right side wall structure, and is used as a longitudinal edge beam of the ceiling structure, and then bulk parts which cannot be singly combined in the original structure can form the ceiling welding structure; (2) a welding tooling adopting the reverse assembly and outer positioning method is used for positioning and clamping, the welding sequence of the new ceiling structure is adjusted, the welding of a ceiling window frame structure is firstly completed, then the welding of a ceiling skeleton and a front window frame is completed, and finally the welding of a ceiling skin and the skeleton is completed, so a five-shaft processing center can complete processing at one time. The assembly welding process method has the advantages that the existing production technique of the aluminum structure ceiling of the driver cab of the motor train unit is a full new technique, the product quality of the ceiling part is improved, the assembly welding difficulty of the aluminum structure ceiling of the driver cab is decreased, the production cycle and labor intensity of the driver cab assembly are improved, the production modularizing of the driver cab is improved, and the quality is conveniently guaranteed.