Running stability of hydraulic operating system with features of fast response, high flow rate and instantaneous super power greatly influences the normal and high effective action of ultra-high voltage circuit breaker. Mechanism of super-power hydraulic operating system in 1100 kV ultra-high voltage circuit breaker was analyzed to build a united simulation model, including multilevel control valves, accumulators, high-speed hydraulic cylinder buffering system and so forth, to investigate response features of control valves, buffering features of high-speed hydraulic cylinder and kinematic features of open and close action. Meanwhile, the accuracy of the model was validated with test data compared with design criterion, founding that there exist an extremely high pressure up to 107 MPa with a tremendous changing process within the hydraulic cylinder, and the velocity of the piston hitting the cushion sleeve at end of the cylinder was about 1.7 m/s which caused great impact on the sleeve. What's more, three optimal schemes for clearance distribution of the benched trunk piston were put forward to obtain a better cushion result reducing peak pressure and end speed of piston to a rate of more than 30%. Research methods, parameter analysis and optimal design results can act as guidance for further study and performance improvement of hydraulic operating system of ultra-high voltage circuit breaker.