Abstract: Nitrogen fertilizer is one of the major nutrition to Brassica napus L. To assess the influence of nitrogen fertilizer on protein and oil contents of B. napus and expression of their synthesis related genes, A field experiment was carried out under four nitrogen fertilizer gradients, 0, 90, 180 and 270 kg/ha, using B. napus cultivars Zhongshuang 11 and Parter (from Germany). The oil content and protein abundance in matured seeds were investigated. Gene expression profiles of ACCase, DGAT2 and PEPC of seeds at different development stages between nitrogen fertilizertreated (180 kg/ha) and blankcontrol of the two cultivars were set up. The results indicate that the seeds protein abundances are increased and the oil contents are decreased under the higher nitrogen fertilizer levels, and the oil content of Parter is more obviously decreased compared to Zhongshuang 11 Compared the gene expression levels between the treatment and the control, the expression levels of ACCase and DGAT2 have no obvious differences for the two cultivars during 7-25 days after the pollination (DAPs). However, at the 31 DAP, the two genes in Zhongshuang 11 are down regulated 1 and 12 folds respectively, while the two genes in Parter are up regulated 1 fold. The expression peaks of PEPC are all brought forward in the treatments of the two peaks of PEPC are changed from 31 DAP to 13 DAP in Zhongshuang 11 and changed from 13 DAP to 7 DAP in Parter. The results indicate that there are genotype differences in the three genes responding to the nitrogen fertilizer.