Abstract: As a kind of special weak structural plane, shear zone has aroused attention and deep understanding of the influence on engineering construction. Rock mass of dam foundation with shear zone of Guxian hydro-junction project is taken as the research object, this paper analyzed the distribution characteristics of shear zone, and determined parameters of shear strength by large in-situ shear test. In the meantime, according to the established calculation formulae of geological strength index(GSI)for rock masses estimated by ultrasonic velocity of rock mass, the rock mass mechanical parameters are predicted by Hoek-Brown criterion. The result shows that equivalent fraction coefficient from Hoek-Brown criterion is lower than test value and cohesion force is far greater than that from shearing test. It is shown by error analysis that the difference between experiment values and estimated ones is mostly induced by the span of minimum principal stress used in Hoek-Brown criterion. For this situation, some cautions and corresponding resolve methods while using Hoek-Brown criterion are reminded. In addition, the proposed method provides a new approach to determine the mechanical parameters of stratified rock mass with shear zone, when test data are scant.