The selection of mechanical parameters is very important for the stability analysis of rock mass engineering. The value of mechanical parameters of rock mass based on Hoek-Brown strength criterion is affected by the subjective judgment to rock mass engineering geological characteristics. In this study, several parameters such as joint characteristic coefficients and block volume numbers are used to quantify the geological strength index, and the calculation method for the equivalent shear strength parameters of rock mass is obtained by using Hoek-Brown strength criterion. Based on slope analysis, the influences of joint parameters, such as fluctuation coefficient, alteration coefficient and roughness coefficient, on the shear strength parameters at different lithologies are discussed. An engineering case is used to analyze the effects of various factors on the factor of safety of rock slope. The results show that, when the joint alteration coefficient is between 4 and 8, the joint angle between 60° and 80°, the alteration coefficient of joint between 2 m and 3 m, the joint roughness coefficient between 2 cm and 3 cm, the average joint spacing value between 900 mm and 1000 mm, the variation of joint parameters has little effect on cohesion or internal friction angle. When the geological strength index exceeds 70 or the disturbance coefficient ranges between 0.6 and 1, they have a great impact on the mechanical parameters of rock mass and stability analysis results of rock slope. The range of parameters should be increased to obtain more test data and reduce analysis errors.