Different determination methods of mechanical parameters of rocks at home and abroad are contrasted. In-situ tests are made on Mesozoic monzonite and Triassic metamorphic sandstone at dam site. Statistical methods are used in order to determine rock mechanical parameters. Rigid circular bearing plate is used for rock mass deformation test. Then the fitting relationships between the longitudinal wave velocity of rock masses and deformation moduli are established. Method of least square regression is used for deformation data processing. Horizontally pushing lifting jack of direct shear tests are operated on rock mass shear strength test. - center point group analysis is used for treating shear test data. Fault gouge samples obtained from the weak layers are brought to indoor lab physico-mechanical test. Shear parameters of weak intercalated layers gouge are obtained by means of statistical empirical formula in the Technical Code for Investigation of Geotechnical Engineering GB50021-2001. The shearing strength parameters obtained by point groups are generally consistent with parameters obtained by in-situ test. So it is reliable.