The bank slope failure is closely related to the rise and fall of river level generally. In order to analysis the influence of the rise and fall of river level on Jin’an River bank slope stability in Fuzhou, the saturated-unsaturated seepage of bank slope with revetment was modelled based on the engineering geological condition of some bank of Jin’an River, and the effect of rise and fall of river induced by the DRWWOS(Drawing River Water to Wash Out Sewage) project on bank slope stability was studied. The results show the silt lying on the slope toe impedes pore water change, manifesting as in its sphere of influence river water is hard to flow into the bank when river rises, and the pore water pressure can not dissipate in time when drawdown. The faster the river rises, the more stable the bank slope becomes. On the contrary, the larger river level falling rate is more likely to leads to bank slope failure. Due to the poor bank drainage performance, the frequent rise and fall of river level results in pore water pressure increasing further, then impairing the bank slope stability. During DRWWOS project, the river level falling rate control and pore water pressure dissipation must be paid enough attention to. Also, replacing silt lying on the slope toe by good permeable material is a good choice to reinforce the bank slope.