Excessive nitrogen (N) fertilization in wheat season in the Taihu Lake region has resulted in serious environmental problems. Previous studies have recommended optimum N fertilization rate. However, so far no holistic evaluation has been made of environmental impacts of N fertilizer. Therefore, based on experiments on fates of various N fractions in relation to N application rate in the region, an evaluation model for knock-on effect of N was developed, integrating agronomic, environmental, and economic benefits in wheat season in the Taihu Lake region. Evaluation with the model show that N application was recommended at N 205 kg hm^-2 for wheat season in the Taihu Lake region, which may bring about maximum net benefit 2 621 Yuan, which is the balance between 3 722 yuan hm^-2 in yield benefit and 1 101 yuan hm^-2 in total environmental loss. The total loss covers the following losses lined in a decreasing sequence in terms of value, acid rain, greenhouse effect and eutrophication. If the net economic benefit is allowed to fluctuate within the range of 10 yuan hm^-2, the recommended regional mean N application rate would vary in the range from 193 to 218 kg hm^-2, which is 10% to 40% lower than the prevailing N application rate, and nevertheless, would increase the net economic benefit by 5%～15% in the Taihu Lake region. This method not only takes into account agronomic, environmental and economic benefits comprehensively, but also provides reference for eco-farming in other regions or other crops. It is easy for decision-makers and farmers to calculate or recommend N fertilizer rate.