This paper describes a 4-cylinder hydraulic circuit system controlled by a new cross-coupled fuzzy PID,and its leveling algorithm is designed to meet the demand of the loading system for test bed. In order to enable synchronous loading and implement precise leveling control,the output displacement derived from a theoretical model,called˙Zn, is tracked in real-time. Using AMEsim software,the reliability of the scheme designed by master-slave control and fuzzy PID cross coupling control have been confirmed, and have drawn a conclusion that the more serious the inconsistencies of the load for 4-cylinder are, the more size corresponding synchronization errors will be. Further,leveling experiments have demonstrated that the synchronization performance of leveling system can be improved significantly by adjusting the load values for the 4-cylinder so as to meet the demand of its un-synchronization. This paper describes a 4-cylinder hydraulic circuit system controlled by a new cross-coupled fuzzy PID, and its leveling algorithm is designed to meet the demand of the loading system for test bed. In order to enable synchronous loading loading and implement precise leveling control, the output displacement derived from a theoretical model, called˙Zn, is tracked in real-time. Using AMEsim software, the reliability of the scheme designed by master-slave control and fuzzy PID cross-coupling control have been confirmed, and have drawn a conclusion that the more serious the inconsistencies of the load for 4-cylinder are, the more size corresponding corresponding errors will be. Further, cylinder so as to meet the demand of its un-synchronization.