Abstract: In order to test the impact mechanical properties of rock, the amphibolites are subjected to impact loads with different confining pressures (0MPa-6MPa) and strain rates (50s^-1-170s^-1) by using the improved SHPB of 100mm diameter. The SHPB has confining pressure device. Experimental results show that under the same confining pressure, the dynamic compressive strength of amphibolites are strain-rate dependent, and the strain-rate effect can be expressed by linear approximations, so the relationship between the dynamic increase factor and the logarithm of strain-rate is approximately linear. The strengthening effect gets more prominent with the increase of confining pressure at the same range of strain rates. The damage constitutive model of rock under dynamical load based on weibull distribution is established through combining statistic damage model and visco-elastic model. It is found that the theoretical curves and experimental curves are in good agreement, indicating the constitutive model is reliable. It can offer reference for further research on rock mechanical properties and engineering application in underground engineering.