Abstract: In order to improve the nitrogen (N) fertilization efficiency of hybrid middle rice retained regeneration paddies, the N saving effect of nitrogen residue in the previous year on the next year’s first season rice was investigated, with a view to laying a theoretical foundation and a practical basis for a reasonable N fertilizer management strategy in regeneration paddies. In 2021-2023, a three-year positioning experiment was carried out in the winter paddy area of South Sichuan, using the high-quality hybrid medium rice variety ‘Jing 3 you 6150’ as the test material, and setting up the treatments of 0, 25%, 50%, 75%, 100% thinning of regeneration rice and reserving N fertilization for the following year’s first season rice, to shape the N saving relationship between N savings and N conservation of the previous year's first season rice through thinning of regeneration rice at the peak of seedling stage and the different N sinking balance of the paddy caused by the difference of regeneration rice yield. Through the regeneration of rice seedling season sparse hole shaping to regeneration rice yield difference to different N residue in the rice field, to explore the relationship between N residue in the previous year and N saving in the next year's first season rice. This study indicates that N residue is significantly negatively correlated with the yield of regenerated rice. The N dry matter production efficiency of first season rice is 15.48% higher than that of regenerated rice, while the N rice production efficiency and N harvest index are 5.89% and 19.77% lower than those of regenerated rice, respectively. Most of the regenerated rice grain sprout fertiliser (¹⁵N) is absorbed by the first season rice of the current year, indirectly promoting the regeneration of buds and seedlings, and is directly absorbed and utilized by the regenerated rice to a lesser extent, and residues in the soil for the use of the first season rice of the following year. N saving of the following year’s first season rice was highly significantly and positively correlated with the previous year’s N sinking residue (r=0.955^**), and both its paddy sinking residue and N saving of the following year's first season rice increased with the increase of the previous year's regeneration rice thinning rate. The N content of the first season rice in the following year is significantly negatively correlated with the yield of regenerated rice in the previous year. The yield of regenerated rice in the previous year was within the range of 0−4125 kg∙hm⁻², and the N application rate for the first season of rice in the following year can be reduced by 0.11−9.11 kg∙hm⁻² according to the local high-yield N application level. Compared with the first season rice, the N dry matter production efficiency of regenerated rice decreased, while the N rice production efficiency and N harvest index increased. This indicates that the N content of the first season rice in the following year has a synergistic effect with the N sink balance of the previous year. Therefore, increasing the yield of regenerated rice is the key to reducing N sink balance in rice fields.