Water inflow estimation is an important component for mine design.However, in the design of common water inflow prediction, not only the value of permeability coefficient is not accurate enough, but also the impact of rainfall process is not considered, which makes the prediction value deviate from the actual value.In view of the problem of water inflow in the stope under the rainfall condition of Fengshuxia Open Pit in Hainan Mining, the comprehensive permeability coefficient, the permeability coefficient of the overlying soil layer and the local permeability coefficient of the mine pit are calculated by the methods of pit pumping test calculation, seepage calculation inversion and borehole pumping test.The permeability coefficient of the open pit is determined.Based on the monitoring of the rainfall, water level and underground water level of the mine for four months in the rainy season, the characteristics of the water inflow of the mine in the rainy season are analyzed.The water migration process of the mine pit under a continuous rainfall from the 50th to 70th days is calculated, and the seepage mechanism of the change of water inflow in the rainfall process of the open pit in Fengshuxia Open Pit is obtained.The study proposed that for a single rainfall of more than 100 mm, it is necessary to cut off and drain the periphery of the pit to prevent a large amount of surface runoff from entering the pit and increase the pressure of subsequent pumping.The results of this paper can provide engineering reference for the calculation of water inflow in the tropical rainforest area of Hainan.