In order to establish an effective ecological management mode of irrigation and fertilization to reduce non-point source pollution caused by fertilization in paddy fields, nitrogen forms and mass concentrations in surface water and soil water in different soil layers were observed with comparative field trials in an experimental zone in Yuyao City of Zhejiang Province. The variations of nitrogen forms in paddy fields with different irrigation and fertilization modes were analyzed. The results show that in surface water, the average concentration of NH₄⁺-N at seven days after the application of basal fertilizer using the reducing fertilization mode was 46.14% of that using the conventional fertilization mode, while the average concentration of NO₃^--N was 83.62% of that using the conventional fertilization mode. The controlled and mid-gathering irrigation mode coupled with reducing fertilization can prolong the field water storage time, allow nitrogen to infiltrate more rapidly and reserve in the tilth layer, and lead to the improvement of effective utilization of nitrogen, the decrease of the nitrogen concentration in surface drainage, and the decrease of nitrogen deep seepage. High nitrogen concentration of surface water was sustained in four days after fertilization. It is pointed out that drainage should be controlled during this period, so that the loss of nitrogen fertilizer can be avoided and the agricultural non-point source pollution caused by nitrogen fertilization can be alleviated.