An assembly system for inserting a terminal into a housing comprises a parallel robot mechanism, a serial robot mechanism, and an insertion mechanism. The parallel robot mechanism has a support platform on which the housing is held and a plurality of joints. The serial robot mechanism has an end effector connected to the support platform and is adapted to drive the parallel robot mechanism to move. The insertion mechanism is configured to insert the terminal into the housing. The parallel robot mechanism is moved by the serial robot mechanism to an insertion position in which an insertion hole of the housing is aligned with the terminal prior to the insertion mechanism inserting the terminal into the housing. At least a portion of the plurality of joints are locked while the insertion mechanism inserts the terminal into the housing to keep the parallel robot mechanism and the support platform stationary.