Abstract: In order to improve nitrogen use efficiency under water storage pit irrigation condition, a mathematical model on soil nitrogen transformation was proposed with characteristics of single water storage pit and was solved by finite volume method, which was verified by the measured data of soil water content and nitrogen transport under indoor experiment conditions with urea fertigation. The results showed that for single water storage pit irrigating with urea application of 1700mg/L, soil ammonium nitrogen were mainly distributed within the range of 20-70 cm depth, the ammonium content increased gradually during 1-3days and decreased after the seventh day. The soil nitrate aggregated near the water front, the nitrification increased gradually during 1-7days after irrigating and the nitrate content increased gradually within 20-70 cm depth. The simulated results of soil water content, wetting front, ammonium and nitrate content are in proper accord with those corresponding measured data, which indicates that the soil nitrogen transformation model is accurate, and numerical solution with finite volume method is acceptable. The proposed model can be used to simulate the soil nitrogen transformation processes.