Abstract: In order to evaluate accurately the rock strength under different confining pressures, a negative power rock strength criterion was proposed according to the upward convex nonlinear relationship between deviator stress and confining pressure during rock failure. The accuracy of the proposed criterion was compared with Mohr-Coulomb criterion and Hoek-Brown criterion. The results showed that the parameters of the negative power criterion are less sensitive to the range of confining pressure, and the negative power criterion could evaluate rock triaxial strength with higher precision. Meanwhile, the applicability of the proposed criterion was verified by using an extensive database of rock triaxial strength tests from literatures. The results showed that the evaluated strength values were very consistent with the test strength values. Thus, the negative power criterion has good applicability to evaluate the triaxial strength of different types of rock. Furthermore, by comparing with the exponential criterion, regarded as an outstanding criterion in rock engineering, the mean relative errors of the rock strengths evaluated by the two criteria were all within 5%, and the negative power criterion has higher accuracy in predicting rock triaxial strength. The proposed criterion can provide scientific reference for the design of exaction and support in deep rock engineering.