Abstract: A field experiment was carried out using manual loessial soil to study the effect of fertilizer application on biological characteristics and yield of winter wheat at two different densities: low density (90 kg/hm2) and normal density (150 kg/hm2). Normal density had 7 different fertilizer treatments: no fertilizer (CK), phosphorus (PN0), nitrogen (P0N135) and different nitrogen and phosphorus combinations (PN45，PN90，PN135，PN180). Low density had 4 fertilizer treatments: no fertilizer (CK), nitrogen (P0N135), phosphorus (PN0) and nitrogen and phosphorus combination (PN135). The result showed that, under low density, the tiller number of CK (4.1 tillers per plant) was lowest and PN135 (6.9 tillers per plant) was highest. The tiller number of CK was lowest and PN180 was highest under normal density, with the average values being 3.2 and 6.8 tillers per plant, respectively. The total leaf area of PN0 and CK was significantly different from P0N135 and PN135 under low density (P0.05). Under normal density, the total leaf area of PN180 was highest 80.7cm2 per stem) and PN0 was the lowest (44.4cm2 per stem). Under low density, the flag leaf area of CK was lowest and PN135 was highest. There was no significant difference between CK and PN0 under normal density, but they were significantly different with other fertilizer treatments (P0.01). The total leaf area and flag leaf area were significantly correlated with grain yield, with the correlation coefficients being 0.875 and 0.931, respectively. Across the whole growing season, DIFN had a change pattern inversed to LAI, with the value of DIFN being lowest at flowering, while LAI being highest at flowing. DIFN and LAI had significant correlations with grain yield, with correlation coefficients being 0.942 and 0.954, respectively. Under low density, PN135 grain yield was the highest (7605.1kg/hm2). In summary, the optimal fertilizer treatment was PN135 in the experiment.