To investigate the non-destructive critical slope rate and stability assessment method for strongly weathered rock slopes with soil and highly weathered rock, based on Jinan's strata, suitable soil layer parameters for numerical simulation are determined. The strength reduction method is then applied to calculate the critical slope rate of the slope, providing reference for construction. The analytical solution for the slope's safety factor is obtained using the improved Swedish slice method and the slip line field method. These analytical solutions provide essential prerequisties for safety factor applications. Results show that strongly weathered rock experiences failure when the rock strata thickness exceeds half of the slope height or the slope ratio surpasses 1:0.5. The obtained safety factor from the analytical solution tends to be conservative, contributing to enhanced engineering safety. For soil and strongly weathered rock slope, the research findings help identify the failure area, facilitating the design of support schemes.