Aiming at the problems of complex and low efficiency of autonomous obstacle-crossing motion control of transmission line inspection robot, taking a five-arm inspection robot as an example, an autonomous obstacle-crossing motion control method was proposed based on finite state machine theory by planning and analyzing the robot obstacle-crossing action sequence. The motion control model of autonomous obstacle-crossing was established with sensor detection information as migration condition, the autonomous obstacle-crossing movement of robot was controlled; the robot was placed in the line environment for inspection experiment. The results show that the robot can recognize, stably and efficiently cross line obstacles and complete the inspection task, which verifies the rationality of the robot system and the feasibility of the control method of autonomous obstacle-crossing movement.