In order to solve the problems of unsteady working process, large peak buffer force and low buffer efficiency of recoil buffer in weapon launcher, a new type of gradual hydraulic buffer structure is proposed. The mathematical model of the buffer in the buffering process is established. The effects of key structural parameters on the cushioning performance are analyzed. The results show that the buffer stroke, piston rod diameter, piston diameter and piston thickness have great influence on the buffer time, peak buffer force and cushioning efficiency of the hydraulic buffer. The buffer stroke, spring stiffness coefficient and pre-compression have great influence on the buffer capacity. The genetic algorithm is used to optimize the key structural parameters with the goal of improving the buffer efficiency and reducing the buffer force. After the optimization, the buffer efficiency of the buffer reaches 96.84%, and the peak buffer force is reduced to 12.47 KN. Compared with that before optimization, the buffer efficiency is increased by 5.4%, and the peak buffer force is reduced by 1.04KN. This method provides a solution for the smooth design of hydraulic buffers for weapon launchers.