Transport and distribution of photosynthetic carbon is an important part of carbon recycling in the “atmosphere-plant-soil” system, but also the main source of soil organic carbon. The development of stable isotope technology enables quantitative research on allocation of photosynthetic carbon. The ¹³C stable isotope labeling technique, featuring zero radioactivity, uniformly marking, safety and reliability, has been widely used in studies on cycling of organic carbon in soil. As an essential nutrient element for plant growth, nitrogen is closely related to the process of photosynthesis of plants. The effect of nitrogen fertilization on the distribution of photosynthetic carbon in plant-soil system may vary with the crop and soil properties. However, so far no much has been reported in this aspect. The ¹³C stable isotope labeling technique was adopted in this study on law of the distribution of photosynthetic carbon in the plant-soil system using paddy red soil as object. The research on effect of N application rate on distribution of photosynthetic carbon has some important scientific significance to understanding in-depth mechanism of soil carbon recycling and formulating management measures to maintain stability and balance of soil organic carbon. A pot experiment, designed to have two nitrogen treatments, N50 and N100, (50 mg kg^-1 and 100 mg kg^-1) and two groups, one labeled 4 times with ¹³C pulse and the other not, was conducted to quantatively study law of the distribution of photosynthetic carbon in the rice-rhizosphere system at different growth stages (tillering, jointing, heading and filling stage). Based on the difference between the two groups in amount of ¹³C, the amount of ¹³C taken up by rice was calculated. It was found that the aboveground biomass of rice in Treatment N100 was significantly higher than that in Treatment N50 treatment (p<0.05) and in the labeled group, it reached 62.05 grams per pot in the former and 47.82 grams per pot in the latter, a 30% difference; The root biomass of rice in Treatment N100 was also higher than that in Treatment N50. In the late rice growing period, root growth was enhanced in Treatment N50, increasing the root-shoot ratio. The δ¹³C‰ in either shoots and roots reached a maximum at the tillering stage. In shoots it reached 927‰ and 1216‰ in Treatments N50 and N100, respectively, and in roots it did 771‰ and 695‰, respectively. The value was the lowest at the heading stage, and did not vary much between the other growth stages, It varied in the range of 621%~671‰ in the shoots and 559‰~676‰ in the roots. δ¹³C‰ in rhizosphere soil increased gradually with rice growth, and was higher in Treatment N100 than in Treatment N50 in all the growth period except for the tillering stage. Throughout the entire growing period, the net ¹³C input into the shoots varied in the range of 2.31~5.55 g kg^-1 and that into the roots in the range of 2.41~2.82 g kg^-1, but the concentration of ¹³C in the rhizosphere soil was only in the range of 0.004~0.014 g kg^-1. After four times of pulse labeling, the total cumulative amount of ¹³C in the rice plants in Treatment N100 reached 265.5 mg, 39% higher than 191.6 mg in Treatment N50, and 46% higher than the amount in the rhizosphere soil. In the early rice growing season, photosynthetic carbon of rice was mainly transported to the underground part (21.7%~52.7%), but the proportion dropped sharply (7.50%~8.90%) at the filling stage. The nitrogen treatments were more or less the same in distribution ratio of cumulative photosynthetic ¹³C in plant and soil, approximately 72% in the shoots and 28% in the underground part (root 7.21%~7.71% and rhizosphere soil 20.3%~21.2%). Appropriate nitrogen fertilization can increase not only crop yield, but also the amount of organic carbon crop transports to the soil. When nitrogen is insufficient, rice enhances its root growth to absorb nutrients. The distribution ratio of photosynthetic carbon input in rice-rhizosphere system varies with the rice growth stage. Nitrogen application promotes growth of the crop, thus increasing accumulation of photosynthetic carbon, but does not have much effect on distribution ratio of the photosynthetic carbon in the rice-soil system throughout the rice growing period.