The burying nylon mesh bag method was used to study the effects of returning green manure rapeseed to the field in the initial flowering stage(G1)，full blooming stage(G2)and silique maturity stage(G3)on the dry matter decomposition and nutrient release of rapeseed，which provided a theoretical basis for rapeseed applying to reduce nitrogen and increase its efficiency for after-reap crops.The results showed that the dry matter amount returning of G1 treatment was significantly lower than that of G2 and G3 treatments，with a decrease of 45.43% and 46.87%，respectively.The carbon content of G1 and G2 treatments was lower than that of G3 treatment，while the nitrogen and phosphorus content in G1 treatment was the highest，which was 28.17 and 5.21 g/kg，respectively.The potassium content ranked as G1>G2>G3 and had significant difference between G1 and G3 treatments.After returning，rapeseed decomposition was divided into fast，medium and slow stages.The according durations were 0~17，18~45 and 46~123 d after returning，and the corresponding cumulative decomposition rates were 44.27% ～ 66.87%，12.56% ～ 29.18% and 4.49% ～ 13.81%，respectively，with the final cumulative decomposition rate reaching 60.53% ～ 91.87%.There was no significant difference in decomposition rates between G1 and G2 treatments，however they were significantly higher than that of G3 treatment.The nutrient release rates of carbon，nitrogen，phosphorus and potassium corresponding to the decomposition rates of rapeseed after returning also showed a pattern of fast，slow and stable release in three stages，and the cumulative release rates of nutrients in different returning stages were shown as follows:potassium>carbon>nitrogen>phosphorus.After decomposition，the cumulative release rates of carbon，nitrogen，phosphorus and potassium were 94.70%，92.97%，88.76% and 93.26% in G1 treatment，84.25%，86.32%，86.51% and 92.52% in G2 treatment，and 72.52%，59.97%，68.54% and 87.67% in G3 treatment，respectively.The amounts of nitrogen，phosphorus，and potassium release in G2 treatment were the highest，which were 125.15，22.88 and 50.42 kg/hm²，respectively.The former two elements were significantly higher than that of G1 and G3 treatments，and there was no significant difference for the latter one between G2 and G3 treatments.In summary，rapeseed returning in full blooming stage not only achieved the highest dry matter amount，but increased the nutrient releasing amounts of nitrogen，phosphorus，and potassium，which is most suitable returning period.This study can provide technical support and theoretical basis for realizing the replacement of chemical fertilizers and rational use of fertilizers in the next crop.