Aiming at the problems of low nutrient content and poor water retention in irrigated silted soil in Ningxia Yellow River irrigation area，the comprehensive impact of biochar as a kind of soil amendments on improving soil organic carbon pool in this area was revealed. Based on a 12-year long-term positioning experiment，the effects of combined application of nitrogen fertilizer and biochar on organic carbon fractions and carbon pool management index( CPMI)in irrigated silted soil were studied. Four treatments were set up:the control group(CK)，single application of biochar(B，C 9000 kg·hm-2)，conventional fertilization(FP，N 240 kg·hm-2)，combined application of nitrogen fertilizer and biochar(FP+B，C 9000 kg·hm-2，N 240 kg·hm-2). Soil samples were collected and analyzed after wheat harvest in 2023. The results showed that the particle size of water-stable aggregates in each treatment was mainly in the <0.25 mm，and the content of aggregates in>5，1–2 and 0.25–0.5 mm particle sizes was significantly increased under B and FP treatment. Compared with CK，all fertilization treatments had obvious improvement effects in irrigated silted soil. Among them，FP+B treatment had the most significant effect on the increase of soil organic carbon(SOC)content，with an increase of 39.41%；B treatment increased by 25.55%；FP treatment increased by 13.86%. The contents of labile organic carbon(LOC)，microbial biomass carbon(MBC)and particulate organic carbon(POC)were increased by 21.72%–82.83%，10.66%–43.33% and 11.99%–78.65%，respectively；and the change trend of LOC，MBC and POC contents was consistent，the order was FP+B> B> FP> CK.Compared with CK，the content of dissolved organic carbon in FP+B treatment decreased significantly by 41.67%，and there was no significant difference between FP+B and B treatment. Compared with CK，the CPMI of B，FP and FP+B treatments increased by 49.76%，23.03% and 108.25% respectively. Pearson correlation coefficient showed that SOC and CPMI were positively correlated with availaboe phosphorus，microbial biomass nitrogen，MBC，LOC and POC，indicating that available nutrients，microbial activities and activated carbon pool jointly promoted soil carbon cycle in irrigated silted soil. Therefore，it was necessary to clarify the combined application of nitrogen fertilizer and biochar on the carbon pool of irrigated silted soil in Ningxia，so as to provide scientific basis for improving soil fertility and the carbon sequestration potential of regional farmland ecosystem，and provide theoretical reference for the sustainable development of local agriculture and the improvement of cultivated land quality.