The invention discloses an assembly system, which comprises a parallel robot mechanism, a serial robot mechanism and a terminal insertion mechanism, wherein the parallel robot mechanism is provided with a supporting platform, and a shell is kept on the supporting platform; an end effector is arranged on the serial robot mechanism, and the end effector is connected with the supporting platform; and the terminal insertion mechanism is used for inserting a terminal in the shell. Before the terminal is inserted in the shell, the serial robot mechanism drives the parallel robot mechanism to move to enable a terminal jack in the shell to be aligned with a to-be-inserted terminal. During a process of inserting the terminal in the shell, at least partial joints of the parallel robot mechanism are locked, the parallel robot mechanism thus cannot be moved, and the supporting platform is kept still. Thus, the insertion force is completely borne by the parallel robot mechanism with large rigidity and is not applied to the serial robot mechanism with small rigidity, and thus, the shell position precision is ensured, and the terminal assembly precision is improved.