Abstract: Soil moisture directly affects on the vegetation respiration, transpiration, and various chemical reactions, it is an important eco-environmental factor in bionomic meteorology.Rainfall and evaporation are two important turbulent factors affecting soil moisture, qualitative and quantitative theoretical research on them with numerical analysis is important, particularly in semi-arid and arid regions.Evaporation has a constant dissipation effect on soil moisture, it can be regarded as continuous, while discontinuous rainfall has a pulse effect on the humidity.To explain the Rainfall and evaporation influence on soil moisture, this paper established the numerical model that pulse-rainfall and evaporation respond to soil moisture, and get the sufficient condition of the periodic solution in this differential system, with the qualitative analysis.On this basis, with Forcal parameter fitting of the equation and numerical analysis of Maple, we get numerical simulation of this system.