Restoring the degraded grassland is crucial for enhancing the grassland carbon sink and reducing greenhouse gas emissions. Caragana korshinskii (C. korshinskii) have been extensively planted in the degraded grasslands of China for many years, yet its utilization is insufficient. This study investigates the effects of organic amendments on flux of greenhouse gases and on C stock in the degraded steppe. Treatments included a control (CK), application of C. korshinskii biochar (BC), application of phosphate fertilizer (PF), and application of C. korshinskii biochar-based phosphate fertilizer (BP). We analyzed seasonal variation in CO2 and CH4 fluxes at different soil depths, as well as plant community characteristics, soil temperature, moisture and soil microorganisms. The results showed that the total CO2 emission flux increased significantly under BP, reaching 899.394 kg/hm(2) more than CK (789.711 kg/hm(2) ). Compared to CK, the total CH4 uptake flux increased significantly by 0.39 kg/hm(2) under both BP and PF, while the total CH4 uptake flux increased significantly by 0.32 kg/hm(2) under BC treatment. BP significantly increased aboveground plant biomass and soil microbial diversity, and increased Net Ecosystem Carbon Budget (NECB) by 38 g C m(-2) compared to CK. Due to the P addition influence on the relative abundance of Acidobacteria and Planctomycetes, the three fertilization treatments shifted the soil from a CH4 source to a CH4 sink. Overall, applying C. korshinskii biochar-based P fertilizer to degraded grasslands is an effective measure that reduces methane emissions and increase C stock.