By using of the INSTRON electro-hydraulic and servo-controlled material testing machine and adopting low-cycle-index fatigue loading method, the test of rock failure with medium strain rate under dynamical loading had been carried out successfully. This provides a feasible testing method for studying the behavior and constitutive relation of rock failure with medium stain rate under dynamical loading or static and dynamical combination loading. The test results have shown that the average strain rate of test rock specimen increases with the increasing of loading frequency, the strain rate can reach a stable value of 10-2 S-1 as the loading frequency is higher than 0.5 Hz, in the case of uniform loading frequency, within the range of rock elasticity the change of value of static preload has less influence on the average strain rate of test rock specimen, therefore, it could approximately be considered that the same loading frequency will result in the same strain rate.