In order to study the influence factors of working characteristics of gradual throttling hydraulic buffer, its structure and working principle were analyzed. A mathematical model was established based on fluid mechanics and kinematics, and characteristics curve of the buffer was obtained after solved by MATLAB. In order to achieve the better cushioning effect, the buffer was optimized by genetic algorithm. The radius and length of damping hole as well as the minimum radius of needle throttle bar were set as optimization variables, and the difference value between the ideal buffer efficiency and the actual buffer efficiency was set as objective function. The results show that the buffer efficiency is increased and the maximum buffer force is reduced after optimization.