Based on unsaturated soil seepage and shear strength theory , to explore the pore pressure dissipation law , it has been analyzed seepage about slope of deep foundation pit in Xian , supporting by pile-anchor retaining structure under the condition of continuous rainy by MIDAS software . The simulation result shows a temporary saturated region would appear on the surface of slope in continuous rainy days , then soil water content increasing as the rainwater infiltrate into a deeper soil layer gradually .For the sake of different cohesion of different time , Combine moisture filed , coming from pore pressure field , with the functional relationship between water content and cohesion , of simulated with filed test dates .The influence law of continuous rainy is derived from stability analysis by strength reduction fem about slope safety factor and stress of retaining structure .