The natural light degraded grassland in the western Songnen plain was selected as the research object，and six different fertilizer combinations and two mixed sowing ratios of leguminous and gramineous pasture seed were set up to study the effects of interaction of different fertilization levels and mixed sowing ratios of legume-grass on plant community biomass，community composition and forage quality，in order to determine the best rate of fertilizer application and suitable proportion of forage for restoration of natural degraded grassland in this area. The results showed that fertilization and reseeding interaction significantly increased the aboveground biomass and protein content(P<0.05). In the two mixed sowing modes，the aboveground biomass under different fertilization treatments increased by 2.42%-68.51% and 20.21%-60.88% respectively，compared with that of the control treatment. The aboveground biomass of legume-grass in the 2∶2 configuration was higher than that in the 1∶2 configuration. The aboveground biomass of legume-grass in the 2∶2 configuration+N150P0K180(N 150 kg/hm²，P2O5 0 kg/km2，K2O 180 kg/hm²)was 290.68 g/m2，which was 37.75%-94.71% higher than other treatments and the difference was significant(P<0.05). When nitrogen supplemental level was higher than 150 kg/hm²，the aboveground biomass of legume-grass in the 2∶2 configuration decreased. The species richness was higher in the treatments of high phosphorus contentin the 2∶2 configuration. While richness index of N50P40K45 (N 50 kg/hm²，P2O5 40 kg/hm²，K2O 45 kg/hm²) in the 1∶2 configuration was 1.99，Shannon-Wiener index was 1.88，which was significantly higher than those of other treatments(P<0.05). The crude protein content of legume-grass in the 2∶2 configuration was higher than that of 1∶2 configuration，the crude protein content of legume-grass in the 2∶2 configuration+N150P0K180 was 22.64%，which was 26.06%-84.82% higher than those of other treatments，and the difference was significant(P<0.05). There was a significant positive correlation between crude protein content and aboveground biomass(r=0.339，P<0.05). Comprehensive analysis showed that legume-grass in the 2∶2 configuration+N150P0K180 was the best combination to obtain high yield and quality of pasture，legume-grass in the 1∶2 configuration+N50P40K45 was the best combination to restore the species diversity of lightly degraded grassland.