Base on the experience of practical operation and the results of model test, paper points out the features of tensioner hydraulic system and two main troubles that often cause the damage of hydraulic components. The mathematical model of the system is analyzed and the pressure response is calculated with respect to the step input of torque on hydraulic actuator. This calculated result agrees with our experimental result. For overcoming the shortage of pressure impulse, the measure of “prebuilding up pressure” is suggested, which was tested in our laboratory. The test proofs that this measure can effectively prevent pressure impulse caused by starting under full load.