Abstract: To explore a green and efficient double cropping rice system that simultaneously maintains stable yields, enhances productivity, and improves soil nutrient status, a field experiment was conducted based on a mixed cropping system of Chinese milk vetch and oilseed rape. The experiment was designed with five nitrogen (N) application rates: no N application (CK), conventional N application (150 kg∙hm⁻², N1MR), 20% N reduction (120 kg∙hm⁻², N2MR), 40% N reduction (90 kg∙hm⁻², N3MR), and 60% N reduction (60 kg∙hm⁻², N4MR). The effects of different N application rates under mixed green manure sowing on rice yields, dry matter accumulation (DMA) and partitioning, and soil nutrient characteristics were investigated. The results showed that compared with the N1MR treatment, the N2MR treatment increased the actual yield of early rice by 16.1% (P<0.05), and N2MR, N3MR, and N4MR treatments increased the actual yield of late rice by 12.5%, 8.3%, and 6.9%, respectively (P<0.05). The total actual yield of both early and late rice under the N2MR treatment reached 14.5 t∙hm⁻², which was 7.4%−22.9% higher than those under other treatments (P<0.05). In the late rice season, compared with CK treatment, other treatments except the N1MR treatment increased the DMA at all growth stages. During the heading−maturity stage, the DMA of early rice under N2MR and N3MR treatments significantly increased compared with that under other treatments, with increases ranging from 92.1% to 151.7% and from 57.9% to 107.0%, respectively (P<0.05). In addition, the DMA of late rice under the N2MR treatment was 40.3% higher than that under CK treatment (P<0.05). With respect to soil nutrients, compared with CK treatment, the N2MR treatment significantly increased the soil organic matter and ammonium nitrogen content of early rice by 43.8% and 36.1% and those of late rice by 31.6% and 55.3%, respectively, at the maturity stage (P<0.05). Compared with the N1MR treatment, the N2MR treatment significantly increased the soil organic matter content of early and late rice at the maturity stage by 23.3% and 14.9%, respectively (P<0.05), and the soil ammonium nitrogen content of late rice at the maturity stage by 32.7% (P<0.05). Compared with the N1MR treatment, the N4MR treatment increased the soil available potassium content by 109.0%, 57.8%, and 56.9% at the winter crop incorporation stage, early rice maturity stage, and late rice maturity stage, respectively (P<0.05). Correlation analysis showed that actual rice yield was significantly positively correlated with soil total nitrogen content (P<0.05), available phosphorus content (P<0.05), population biomass (P<0.05), soil organic matter content (P<0.01), and effective panicle number (P<0.01), while showing a significantly negative correlation with soil pH (P<0.05). Overall, under mixed sowing of green manure, a 20% reduction in nitrogen application (N2MR) effectively balanced yield improvement and soil fertility enhancement, representing a sustainable nitrogen management strategy for achieving high yields and high efficiency in double cropping rice systems.