Abstract: The strength of rock-like materials has obvious strain rate effect. Based on the characteristics of uniaxial dynamic strength, a simple strength criterion is proposed, which can uniformly predict the uniaxial strength from quasi-static to dynamic. Under the framework of the unified strength criterion, the triaxial dynamic strength criterion is studied. In the double-logarithmic coordinate system, the meridian strength envelopes at different strain rates are approximately parallel. The effects of friction, hydrostatic pressure and intermediate principal stress of the materials are not affected by the change of strain rate. Thus, a dynamic coordinate system is established, and the unified strength criterion is extended to consider the strain rate effect. Based on the obtained criterion, the uniaxial compressive and tensile strength are investigated. The strength criterion will represent similar characteristics to those obtained by uniaxial tests. Finally, the strength criterion is verified by strength tests of concrete. By fully understanding the dynamic strength characteristics, the parameters in the proposed strength criterion have clear physical meanings, and can provide a theoretical basis for dynamic response analysis.