Abstract: On the basis of the Xiluodu Project and the Ertan Project,the method for calculating the reliability of the HoekBrown empirical strength criterion and the sensibility of the reliability of the criterion to the variation coefficients of parameters (such as m,s) are presented in this paper.Besides,the influence of the middle principal stress on the reliability for the 3 D HoekBrown empirical strength criterion is analyzed and discussed.Finally,the conclusion is that the variability of the strength parameters is one of the decisive factors affecting the reliability of the criterion.From this paper,it is known that the detailed survey and the experiment as well as the statistic analysis are important to the technical design.