Due to the growing deficiency of water resources and non-point pollution caused by nitrogen leaching losses from paddy fields in China, a field case study was conducted to investigate the dynamic characteristics and the load of nitrogen leaching losses under different water and fertilizer managements by setting two kinds of irrigations and four kinds of nitrogen levels. Results showed that-N concentration in the leachate was positively correlated to N application rate at 20 cm soil depth, -N concentration reduced by 2%-35% when N input reduced,-N concentration did not correlated with N application rate at 80 cm soil depth. -N concentration were both positively related to N application rate at the above two depths. Control irrigation increased -N concentration significantly by 31%, and water leakage was less than traditional irrigation; however -N leachate was 16%-49% lower. Nitrogen was leached away mainly in the form of-N, and it was 77%-92% of total nitrogen leaching flux. Reducing nitrogen application rate decreased-N leaching flux by 14%-56%. Controling irrigation and reducing nitrogen application rate could coordinate economic benefit and water environmental benefit of nitrogen application well, and it would be environment-friendly water and fertilizer management methods for Taihu Lake region.