The change of the bank slope accumulations’seepage and its stability is a dynamic process during the period of rising or falling of reservoir water level. The combination of the FEM method and equilibrium analysis was applied to analyze the action mechanism and laws of the water level’s rising and falling speed effect on accumulations’seepage and stability. The analysis results showed that the water level’s rising and falling speed can influence the congeries’s transient seepage obviously, and faster rising speed of water level is favorable to the accumulations’stability. But the faster falling speed is unfavorable, and the stability coefficient will reduce by 15%~20% with the falling speed increased from 0.5 to 5 m/d, and the most dangerous water levels are commonly located at one-third to one-fifth of the congeries’s height up the accumulations’ bottom.
