To improve the yield of rapeseed under different sowing dates by direct sowing, the effects of hydro? gen peroxide (H2O2) seed soaking were studied especially on late-direct seeding. In 2017, an open-air experiment was carried out using rapeseed cultivar Nannongyou 4. Seeds soaked with H2O2 (0.05%) was sown in 2 sowing dates (early sowing on October 5, 2017, late sowing on October 25, 2017 ) to observe the photosynthetic characteristics and the growth and development dynamics of rapeseed during the wintering period. The results showed that: (1) late sowing prolonged the seedling stage and shortened the bud-bolting stage, reduced the available accumulated tem? perature before flowering from 1349.5°C·d to 1095.5°C·d, and reduced the accumulation of dry matter during vege? tative growth period of rape; late sowing increased the accumulated temperature of reproductive growth period, which was 1119.5 d higher than that of early sowing at 1042.5°C·d. As the growth period of late sowing was short? ened, the accumulated temperature of activity was reduced, and the accumulation of dry matter was reduced, result? ing in a significant yield reduction of 8.3%. (2) Soaking with H2O2 had no significant effect on germinating seedlings and aboveground biomass of early-sowing rapeseed, but significantly inhibited underground biomass and photosyn? thetic capacity, reduced dry matter accumulation during overwintering period, and then affected yield formation in later period, resulting in significant yield reduction of rapeseed, with a decrease of 10.9%. (3) Soaking with H2O2 promoted the germination of late-sown rapeseed seedlings, increased leaf area, and promoted the accumulation of
dry matter in rapeseed, which increased the yield by 15.7%. Therefore, under the condition of late direct seeding,the yield of rapeseed could be increased by soaking seeds with H2O2.