Rockmass strength parameter is an important mechanics index in major engineering. Now many empirical rela-tionships for this parameter based on that of rock often occurs index determination difficulty and inaccurate estimating results. Fuzzy discount method for rockmass strength parameter getting from corresponding rock is introduced in this paper, and then, a deep cut slope is selected as a case, basing on rock mass quality characteristic data from in situ investigation, the rockmass strength parameter is predicted by fuzzy evaluation and verified by in field test results.