In order to make up for the shortcomings as low control accuracy of traditional manual operation of a certain type military impact bridge, study the motion trajectory planning and automatic control technology of the bridge. First the space trajectory model of the bridge was built based on trajectory planning target, and the numerical analysis was carried out.Then the relational model of joint angle and control cylinder was established, and the bridge attitude was converted to co-control stroke of bridge cylinder for place and extend. Finally cylinder was controlled to motion according to the planning stroke with the help of the software programming of the electric control system, so as to complete the automatic control operation of the bridge. The results show that the trajectory planning and automatic control technology can meet the requirement of anticollision, and improve the smoothness, speed and safety of the bridge erection operation.