Abstract: In view of the high-speed and lightweight characteristics of sorting robots, some lightweight and slender rods produce flexible deformation under high-speed working conditions, which affects the overall motion stability of the robot, and even affects the sorting efficiency in severe cases; so it is necessary to analyze its motion stability. First, three-dimensional modeling software is used to model the sorting robot and analyze the structure. Then, the ABAQUS and ADAMS are comprehensively applied to conduct the rigid-flexible coupling simulation analysis, so as to analyze and compare the motion characteristics of the rigid model and the rigid-flexible coupling model at different speeds. The results show that speed is an important factor affecting the stability of the sorting robot. With the increase of sorting speed, the error of displacement, speed and acceleration becomes larger; and the sorting speed has the greatest influence on the acceleration, followed by speed, and minimal effect on displacement. It provides a theoretical basis for the related optimization of the sorting robot.