Abstract: The identification and study of crack initiation stresses are of great importance for understanding the load deformation and damage processes in brittle rocks. This paper systematically summarizes the existing methods for determining crack initiation stress (crack volume strain method,lateral strain method,moving point method,acoustic emission ringing counting method) and their problems,and proposes a method for evaluating crack initiation stress in brittle rocks based on the evolution of acoustic emission b-value. A series of uniaxial loading tests on meta-gabbro and granite were carried out using the GAW2000 uniaxial rigidity testing machine and acoustic emission tester,and the proposed and existing methods were evaluated based on the mechanical and acoustic emission results. The results show that the acoustic emission b-value evolution method has a clear physical mechanism and meaning,can easily and accurately determine the magnitude of the initiation stress,and the measured stress results are consistent with those obtained by the existing methods. The analysis of variance shows that there is no statistical difference between the proposed method and the existing method,which verifies the reliability of the method in determining the crack initiation stress. The crack initiation stresses of both rock samples were positively and linearly correlated with the uniaxial compressive strength,and the crack initiation stresses determined using the proposed method were about 0. 51 times of the uniaxial compressive strength for meta-gabbro and 0. 48 times of the uniaxial compressive strength for granite. The proposed method and its findings are valuable for enriching the means of rock crack initiation stress testing and exploring the mechanism of brittle rock damage.