The actuator of the stepless capacity control system of a reciprocating compressor directly controls the action characteristics of the suction valve, thus changing the regulation system energy-saving effect and the operating performance of the compressor. Optimizing the structural and control parameters of the actuator can reduce the withdrawal impact of the valve plate and improve valve performance. As a mechatronic hydraulic system, the capacity control system has the characteristics of multi-system coupling, system structure and interrelated control parameters. This paper improves the operating model of the reciprocating compressor under the condition of capacity control and integrates the coupling effect between mechanical and hydraulic systems and the valve. The solution was solved using a multi-software co-simulation method and the correctness was verified through comparisons with experimental data. The effects of reset spring stiffness, actuator stroke, and return oil pressure on valve action characteristics, compressor performance, and energy-saving effect were analysed. The valve plate withdrawal speed, and the compressor performance parameters, such as operating pressure, standard capacity, indicated work, and indicated specific work as evaluation indexes, and the optimum design scheme of reset spring stiffness, actuator stroke, and return pressure is proposed. The results indicated that, under the premise of guaranteeing control effect and compressor performance, the capacity control system of the reciprocating compressor with optimized parameters reduces valve plate withdrawal speed by 10.8%, improves valve performance, saves energy, and reduces unit maintenance costs.