Abstract: A field experiment was carried out in the south part of Loess Plateau with 632mm precipitation and eight winter wheat varieties, “NR9405”,“9430”,“Yanshi No.9”,“Xiaoyan No.6”,“Shan229”,“Xinong2208”,“Aifeng No.3”and “Shang188”were used as indicating crops to study the effects of nitrogen fertilizer on the yield components of different genotypic winter wheat. The results show that there is a significant difference of ears per unit area, kernels per unit area,tillers per plant,proportion of tillers in the total ears at maturity, kernels per spike,1000 kernel weight, grain volume, grain bulk density, yield per unit area among different genotypic winter wheat. The application of nitrogen fertilizer has a positive effect on plant spike, grain yield per unit area, 1000 kernel weight, and has no significant effect on harvest index. Increase of spike per unit area and valid tillers per plant causes the decrease of 1000 kernel weight; also increasing kernel volume causes the increase of 1000 kernel weight. Spikes grains, tillers per unit area, proportion of tillers in the total areas, kernel weight per plant are the main factors affecting the wheat's yield.