The municipal solid waste landfill is the main place to hold the waste soil and slag. Due to the difference between the filling material and the compaction method, it is of practical significance to study the influence of initial seepage field on the calculation of rainfall infiltration characteristics and stability of the municipal solid waste landfill. Therefore, taking the municipal solid waste landfill in BuJiuWo, Shenzhen as the research object, a numerical calculation model was established based on the unsaturated seepage principle and unsaturated soil strength theory. The calculation schemes of different initial seepage conditions and rainfall intensity are designed, and the seepage characteristics and the variation law of safety factor of the slope under rainfall are revealed. The results shown that the initial seepage field and rainfall intensity have significant influence on the rainfall infiltration characteristics and stability of the municipal solid waste landfill. The peak value of vertical velocity and the rise rate of pore water pressure are positively correlated with the initial matrix suction. When the rainfall intensity is 3.5mm/h, the saturation time of monitoring point 1 is 10.9h, 20.2h and 25.5h when the initial matrix suction is -25kpa, -50kPa and -75kpa, respectively. There is a positive correlation between rainfall intensity and velocity of flow, volume water content and pore water pressure in vertical direction. When the initial matrix suction is -25kpa and the rainfall intensity is 3.5mm/h, the safety factor of the waste dump slope decreases obviously, so necessary engineering measures need to be taken.