In view of the poor welding quality caused by the motion interference between the exhaust pipe and the welding fixture, and the life of the clamping mechanism reduced due to the unreasonable selection of the working cycle of the clamping mechanism. A four claw welding fixture is designed by CATIA software. The device is mainly composed of clamping mechanism and indexing mechanism. The model is imported into ADAMS simulation software for kinematics simulation, and the simulation results of displacement and angle of clamping mechanism and indexing mechanism, as well as the data results of motion speed, acceleration and displacement of four clamping claws in clamping mechanism under different working cycles are obtained. These results provide theoretical basis for solving the motion interference problem of welding fixture and reasonably selecting working cycle, thus the design cycle and cost of welding fixture are saved, and the reliability of welding fixture is improved.