【Objective】Winter multiple cropping of green manures such as Chinese milk vetch and rapeseed is a traditional system for improving soil fertility and crop yield in the rice field in southern China. Thus, it is of great importance to analyze the soil carbon (C) cycle and the ecological functions of green manure by exploring the distribution of photosynthetic C in a rice-soil system under long-term winter cropping of green manure. 【Method】In this study, based on a 38-year rice-rice-green manure cropping experiment, the 13C-CO2 pulsing labeling technology was used to study the distribution characteristics of photosynthetic C in a rice-soil system at the tillering stage of early rice season under long-term green manure (Chinese milk vetch, rapeseed and winter fallow). At the same time, the stability of 13C-photosynthetic C in soil was studied by measuring the content and distribution ratio of 13C in particulate organic carbon (POC) and mineral associated-organic carbon (MAOC). 【Result】The results showed that the biomass of rice at the tillering stage was not significantly changed but the root/shoot ratio was decreased by 12.6%-19.4% with the long-term multiple cropping of green manure. Compared with winter fallow treatment, the cropping of green manure promoted the distribution of 13C-photosynthetic C in the shoot of early rice, and the accumulation of 13C-photosynthetic C was increased by 19.9 mg?plant-1 and 80.6 mg?plant-1 in cropping of Chinese milk vetch and rapeseed treatments, respectively. The 13C-photosynthetic C accumulation in the root of early rice was decreased by 2.7 mg?plant-1 under Chinese milk vetch treatment, while it was not significantly affected by rapeseed treatment. This result infers that long-term multiple cropping of green manure increased soil nutrient supply and reduced the ratio of root to shoot of early rice, which allows the rice to distribute more biomass to the shoot. Meanwhile, the cropping of Chinese milk vetch and rapeseed treatments reduced the distribution of 13C-photosynthetic C in the soil by 7.6 mg?plant-1 and 7.8 mg?plant-1 respectively. The proportions of rice 13C-photosynthetic C to POC and MAOC were not significantly affected by the cropping of Chinese milk vetch, but the proportion of 13C-photosynthetic C in POC was increased by 35.3% with multiple cropping of rapeseed. 【Conclusion】The long-term multiple cropping of green manure promoted the accumulation of rice photosynthetic C in the plant-soil system. Compared with winter fallow treatment, the accumulation of photosynthetic C in the rice-soil system increased by 3.7%-28.0% in cropping of Chinese milk vetch and rapeseed treatments. On the other hand, the long-term multiple cropping of green manure increased the distribution of photosynthetic C to the shoot of rice and reduced the proportion of photosynthetic C to the root of rice and soil. Moreover, the stability of rice photosynthetic C in soil was weakened by multiple cropping of rapeseed treatments. From the perspective of increasing the total organic carbon and the stability of photosynthetic carbon, the cropping of Chinese milk vetch treatment is a better system for winter multiple cropping of green manures.