Abstract: Flow and distribution of farmland water were simulated using Fluent simulation technology and isotope tracing method.Fluent isotope labeled component transport model was set up.Dynamic parameters such as viscosity，osmotic pressure and average velocity of farmland water flow were input in the boundary condition.Water flow state was simulated by using isotope 18O tracer method.Chemical evolution law of farmland water was predicted using reverse hydro geochemical modeling technique.It provided theoretical basis for water pollution control in farmland.