The deformation modulus of rock mass is often estimated by empirical formulas in rock mass engineering. There are many empirical formulas in rock mass classification system, but few studies are found on the statistical characteristics of the results using different empirical estimation formulas and the weight analysis of independent variables. In this paper, the Monte Carlo method is used to analyze the statistical distribution of the deformation modulus estimated by different emperical formula and the weight of the independent variables based on GSI system. Besides, impacts of different disturbance factors are discussed. The results show that the disturbance factors play different roles in the statistical distribution modes of rock mass deformation modulus. The disturbance factor has the greatest impact on the statistical models of rock mass deformation modulus obtained by Hoek formula and the high quality rock mass is less affected compared with that of poor quality rock mass. © 2020, Science Press. All right reserved.