Abstract: Based on the underwater reef blasting project near an ancient landslide in Wanzhou Port,Chongqing,a reliability analysis method for slope stability was proposed by considering the randomness of rock-soil mechanical parameters and the cumulative damage effect of blasting. The method integrates acoustic testing technology,the Slime Mould Algorithm（SMA）,and Monte Carlo（MC）simulation. Acoustic testing was first used to characterize the deterioration degree of the rock mass.Then,SMA was introduced to search for the critical slip surface. Finally,MC simulation was employed to evaluate the failure probability of the slope. The results show that the stability coefficient F_s of the ancient landslide under natural conditions is 1.261,which is close to that obtained by the traditional limit equilibrium method,indicating that SMA is feasible for slip surface search. Under the present model conditions,the slope is generally in a stable state. the physico-mechanical properties of the rock mass deteriorate nonlinearly,and the first three blasting events cause the most significant damage. Under repeated blasting disturbance,the stability coefficient decreases from 1.261 to 1.081,with a reduction of 14.2%. MC simulation shows that the average failure probability P_fincreases to 13.68% after blasting,indicating a markedly increased risk of instability,and reinforcement measures should be taken on site. This method has been successfully applied in engineering practice and can provide a reference for the stability evaluation of similar water-involved ancient landslide projects.