[Objective] The effects of fertilization and mixed sowing on soil nutrients and pasture yield of degraded grassland in the Songnen Plain, Western Heilongjiang Province were studied, in order to provide a scientific basis for restoration of natural degraded grassland in local area. [Methods] The study was conducted on a natural lightly degraded grassland in the Songnen Plain of Western Heilongjiang Province. Astragalus adsurgens and Elymus dahuricus were used as reseeding grasses. Treatments consisted of two interrow mixed sowing ratios 〔legume:grass ratio 2∶2 (B₁) and 1∶2 (B₂)〕,and six nitrogen, phosphorus, and potassium application rate combinations: N₅₀P₄₀K₄₅(A₁), N₁₀₀P₂₄₀K₂₂₅(A₂), N₁₅₀P₀K₁₈₀(A₃), N₂₀₀P₁₂₀K₀(A₄), N₂₅₀P₈₀K₂₇₀(A₅), and N₃₀₀P₂₀₀K₉₀(A₆), where subscripts after each element indicated the application rate given as kg/hm² N, P₂O₅, and K₂O, respectively. [Results] Fertilization significantly improved available nutrients and pasture yield based on the ratio of mixed sowing. Soil nutrient changes in the surface soil layer (0—10 cm) were more affected by fertilization and mixed sowing than in the deeper layer (20—30 cm). Fertilization, mixed sowing, and their interaction had significant effects on the content of available soil nitrogen (p＜0.05). The variation trends of available nitrogen and available phosphorus in the 0—10 cm soil layer were basically consistent with the additions of nitrogen and phosphorus. The contents of total nitrogen, available nitrogen, and available phosphorus in the 0—10 cm soil layer of legume-grass mixture in the 1∶2 ratio were greater than in the 2∶2 ratio at the same fertilization level. The productivity of the high nitrogen treatment (A₆) was significantly (p＜0.05) greater than that of the other treatments. The greatest aboveground biomass values were observed for the legume-grass 2∶2 ratio + N₁₅₀ P₀K₁₈₀ treatment combination (290.68 g/m²) and for the legume-grass 1∶2 ratio + N₃₀₀P₂₀₀K₉₀ treatment combination (254.31 g/m²). [Conclusion] Considering pasture yield and changes in soil nutrients, the legume-grass mixed sowing in the 2∶2 ratio and the fertilizer application rate of 150 kg/hm² for nitrogen can be recommended.