According to experimental data fragments by the principle of close precision, namely, close number of test blocks, and based on mathematical statistics theory, we derived formulas for calculating the statistical parameters of the frictional coefficient and cohesion of rock foundations directly from the normal stress and shear stress on the shear plane of each block in the in-situ shear test. The method takes into consideration the correlation between frictional coefficient and cohesion. In subsequence, in line with the random simulation method of probability theory and the orthogonal transformation theory of linear algebra, we proposed a computational random simulation evaluation method for verifying test block methods according to the characteristics of shear test. The method can also be applied to the verification of other probability statistical methods of frictional coefficient and cohesion considering the discretization of shear strength of test blocks. By applying the computational random simulation method, we evaluated some test block methods and verified the validity of the proposed formulas. We also discussed the total number of minimum test blocks for the test block method. Finally, shear strength parameters of some engineering examples are analyzed statistically, and some statistical characteristics of friction coefficient and cohesion are given.