In order to clarify the input threshold of nitrogen fertilizer in the wheat season in Chaohu Lake Basin, the effects of different nitrogenous fertilizer levels (treatments of N0, N1, N2, N3, N4 and N5, applicated 0, 157.5, 210.0, 262.5,310.0,420.0 kg/hm2) on yield, nitrogen accumulation in plant, nitrogen utilization, residual inorganic nitrogen amount in 0—20 cm soil and nitrogen loss in runoff were studied. At the same time, regression model was used to fit the correlation between them. The results showed that: (1) Compared with no nitrogen fertilizer, nitrogen fertilizer increased wheat yield, and the yield increased by 64.8% in the treatment of N3, which was the maximum. While, wheat yield declined when applying nitrogen fertilizer over 290.9 kg/hm2 through the analysis used quadratic function. (2) Nitrogen accumulation in plant and nitrogen use efficiency both showed a trend of increasing first and then decreasing with the increasing of nitrogen application, and when the actual nitrogen application amount was 296.6 kg/hm2, the nitrogen accumulation amount in the aboveground of wheat was the highest, and nitrogen utilization efficiency was the highest when the nitrogen application was 158.5 kg/hm2. (3) With the increasing of nitrogen application amount, the residual inorganic nitrogen in 0—20 cm soil and the nitrogen loss in runoff both increased gradually, but there was no significant change before nitrogen application amount was 310.0 kg/hm2. However, when the application amount reached 420.0 kg/hm2, the residual amount of inorganic nitrogen and nitrogen in runoff changed obviously, with an average accumulation amount of 67.0 kg/hm2 and an average loss rate of 8.3 kg/hm2. Therefore, when the nitrogen application amount was too high, it would increase the risks of soil inorganic nitrogen residues and nitrogen loss in runoff, and cause pollution to the environment. Combined with soil fertility conditions in Chaohu Lake, considering the effects of integrated fertility test and application amount on wheat yield, nitrogen accumulation in plant, nitrogen use efficiency, residual inorganic nitrogen in soil and runoff loss in this study, we thought the input threshold of nitrogen fertilizer was 157.5 to 262.5 kg/hm2.in Chaohu Lake Basin.