A total of 10 groups of field trials on N fertilizer application rate for winter oilseed rape were conducted in the main production areas of Jiangsu and Zhejiang provinces in 2008-2009 and 2009-2010 to explore responses of the crop in seed yield, dry biomass, N uptake and accumulation, and N fertilizer use efficiency, for modeling of appropriate N fertilizer application rate under the current production condition. Results show that the crop responded significantly to N fertilization in seed yield. When 270 kg N hm^-2 was applied, the mean yield was increased by 1 265 kg hm^-2 or 121% over the control (treatment without N fertilization), reaching as high as 2 581 kg hm^-2. Nitrogen fertilization also improved considerably shoot biomass, N uptake and accumulation of the plant. However, excessive N fertilization led to decline in harvest index and N harvest index of the crop, and hence in the N fertilizer use efficiency. The regional mean optimal N fertilizer application rate (RMONR) was 199 kg hm^-2 under current production condition in our study. The use of the average may not only reduce by a large margin the use of N fertilizer, but also ensure a relatively higher regional rapeseed yield level and N fertilizer use efficiency level. Hence, the currently recommended N application rate, N 200 kg hm^-2, is appropriate and may be subject to slight adjustment in light of the specific conditions of a region or field.