Abstract: Considering that the mechanical parameters of rock mass in reservoir slope are degraded by water level fluctuation and acid rainfall, uniaxial and triaxial compression tests are conducted on the argillaceous sandstone under wetting-drying cycles in acidic environment. Based on the laboratory test results, the uniaxial compressive strength, elastic modulus, material constants and cohesion of rock mass in geological strength index (GIS) are obtained using the generalized Hoek-Brown criterion. The results show that the deterioration of the mechanical parameters is more obvious under higher wetting-drying cycle number and more acid solution for the broken argillaceous sandstone. Under the same GSI score system, there are differences in the ordering of deterioration effect for each mechanical parameter with change of pH values and wetting-drying cycle numbers, the elastic modulus belongs to the largest comprehensive degradation effect, and the cumulative degradation effect of cohesion is the most obvious. A strong linear correlation is observed in the deterioration of mechanical parameters of rock mass, pH value of soak solution and logarithm of wetting-drying cycle numbers. Based on the above research, a three-dimensional curved surface equation for the mechanical parameters of argillaceous sandstone, pH value and wetting-drying cycle numbers is put forward, which can provide a theoretical basis for obtaining the mechanical parameters of rock mass under wetting-drying cycles in acidic environment and predict the stability life of the slope.