To elucidate the regulatory mechanisms of organic fertilizer substitution for chemical fertilizer on soil organic carbon pools，their components，and rice yield in reclaimed farmland，a four-year(2019—2022)field positioning experiment was conducted with five treatments:no nitrogen(N)fertilizer(DM0)，chemical fertilizer alone(100% chemical N，DM1)，40% chicken manure N+60% chemical fertilizer N(DM2)，40% vermicompost N+60% chemical fertilizer N(DM3)and 40% rapeseed cake N+60% chemical fertilizer N(DM4). The results showed that:(1)Organic N substitution treatments increased rice yield by 5.05%-9.83%，compared to DM1 treatment. Among the treatments，DM3 and DM4 treatments significantly outperformed DM2 treatment，with yield increases of 4.03%-4.54%.(2)Organic N substitution improved soil physicochemical properties:soil bulk density decreased by 0.05-0.18 g/cm3，pH increased by 0.22-0.33 units，and the contents of soil organic carbon(SOC)，total nitrogen(TN)，alkali-hydrolyzable nitrogen(AN)，available phosphorus(AP)and available potassium(AK)were significantly increased by 6.92%-24.62%，10.00%-32.22%，15.78%-22.49%，7.45%-13.72% and 8.92%-25.14%，respectively.(3)In terms of soil carbon pool components，significant accumulation was observed in dissolved organic carbon(DOC)，readily oxidizable organic carbon(ROC)，particulate organic carbon(POC)and microbial biomass carbon(MBC)，which increased by 13.07%-31.26%，47.68%-71.68%，57.89%-133.33% and 7.96%-131.76%，respectively. Humic acid(HA)，humin(HUM)and total humus(HDM)were also increased significantly by 11.59%-18.75%，13.13%-20.37% and 18.03%-24.75%，respectively. Random forest model analysis revealed that SOC，TN，DOC，POC，AN，AP，ROC and AK were the key driving factors for yield improvement，with contribution rate of 7.77%，7.65%， 6.81%，5.12%，5.00%，4.50%，4.23% and 4.16%，respectively. In conclusion，40% organic N substitution optimized soil physicochemical properties and expanded the active carbon pool，thereby increasing rice yield. Among the organic fertilizers，vermicompost and rapeseed cake demonstrated superior comprehensive improvement effects，providing a scientific basis for enhancing soil fertility and achieving agricultural carbon neutrality in reclaimed farmland.