Rain Infiltration is the main source to recharge groundwater in the plain regions,and 50%-80% of the total recharge come from it.Much research work about this has been done by many authors,and abundant information has been obtained.The major methods for this subject are 1.Trend analysis,2.Lysimeter and,3.Water balance analysis.Each of them has its own advantage and disadvantage.In order to improve the above methods,the simulation method for rain infiltration was adopted in this paper,The function of F=f(P,A) was established through experiments,then groundwater recharge from the infiltration of rain was calculated from the equation Fg=F-△ψ·r·△H/10 There:F=amount of infiltration P=amount of pricipitaion A=rate of precipitaion Fg=groundwater recharge from the infiltration of rain △ψ=deficit of soil moisture r=weight in cubic units H=depth of deficit of soil moisture.The comparison of the results by our method with actual observation shows good agreement.Method and steps of experiments was also introduced in this paper.