Abstract: Dynamic biaxial compressive test of 71 cubic concrete specimens was carried out on the static-dynamic hydraulic servo triaxial test system designed and manufactured at the Dalian University of Technology.The lateral pressure was kept in proportion to the main axis with the ratio of 0:1,0.25:1,0.5:1,0.75:1,1:1 respectively.The strain rate was 10^-5/s,10^-4/s,10^-3/s,10^-2/s,respectively.The variation of fracture mode and the ultimate strength with different stress ratios and different strain rates was studied systematically.Test results show that the dynamic strength increases as the stain rate increases,and that the damage pattern and the ultimate strength are closely related to the magnitude of lateral pressure exerted on the specimen.A unified formula is proposed to reflect all the factors that affect the dynamic properties of concrete under biaxial loading state.