Based on the theory of dual-cycling water resources, the irrigation water movement module, command loop of land phase of hydrological cycle, paddy field water balance module in SWAT model and the calculation method of rice yield were improved to establish a new distributed hydrological model on the basis of SWAT. The module of canal seepage was added to further improve the new model. The updated model was applied to analyze hydrological cycle for Renminshengli irrigation area in Henan Province. The model was calibrated and validated by E and R2. The result indicates that the improved SWAT model is well adapt to the simulation of water cycling. The improved model can be applied to water resources and water environment of the area with strong human activities, and a new method is supplied for irrigation hydrology.