A two-stage evaluation method was proposed to obtain the values of mechanical parameters of the fractured rock mass. The isotropy and anisotropy state of the fractured rock mass was evaluated through the three-dimensional distribution of mechanical parameters, and two types of calculation models were adopted respectively; the KolmogorovSmirnov (K-S) test was used in hypothesis testing of the probability distribution model of mechanical parameters, and the confidence interval of the data which has passed the hypothesis test was determined, so that calculated parameters could be obtained within the given confidence interval range. A case of excavation simulation for an underground chamber engineering project was conducted using this method. The result indicates that the calculated displacement values agree well with the measured values.