Abstract: With experiment data under different water and nitrogen treatments,this paper studies the changing patterns of nitrogen nxwement and transformation,losses of amrmnia wlatilization and nitrogen leaching,nitrogen distribution within rice plant,nitrogen balance in paddy fields. The results shows that amrmnia wlatilization is high under water saving irrigation (WSI) compared with continuous flooding (CF) because the soil solution concentration is higher. Although concentration of NH₄ and NO₃^- in the percolation water is higher under WSI,total nitrogen leaching loss is lower because the total percolation loss is much lower than those of CF. Under WSI conditions,more nitrogen supply splits can decrease nitrogen losses and increase nitrogen efficiency. WSI practice is propitious to nitrogen recovery and its transferred to grain. The WSI regime produces optimal water and fertilizer management for paddy rice when 250-400 kg/hm² of urea is applied through three splits.