In order to improve the salvage success rate and safety of the spacecraft return capsule under high sea conditions, a method of flexible side salvaging system was introduced. Aiming at the problem of salvaging stability and security of the interceptor arm caused by the rescue ship movement, a method to control the rolling motion of the interceptor arm with the variable amplitude oil cylinder of the crane as the actuator was proposed. Model test studies on horizontal attitude salvage compensation system were conducted by using traditional PID control methods and fuzzy PID control methods. The rolling motion of the model test system was simulated by a swing table. Results show that the traditional PID control is influenced by the reverse dead zone of electro-hydraulic proportional directional valve, and the retraction delay of the variable amplitude oil cylinder cannot be compensated in time, which seriously affects the salvaging efficiency. However, fuzzy PID control can greatly improve the control performance. The model test system has the characteristics of fast response and stable and reliable operation. The compensation accuracy of the simulated six-level sea condition is ±1.3 degree, which can meet the requirements of salvage under high sea conditions. The method theory and test data can provide reference for the control optimization design of prototype.