The improvement and utilization of saline soil is of great significance for maintaining food security in China. The effects of desulfurized gypsum application on labile organic carbon content and enzyme activities in saline soil were investigated using a 2-year field site-specific experiment. The experimental treatments were 0 t·hm-2 (S0)，2 t·hm-2 (S2)，4 t·hm-2(S4)，and 6 t·hm-2(S6)of desulfurized gypsum application. Soil samples were collected from 0-20 and 20-40 cm soil layers to determine the contents of soil labile organic carbon fractions，including dissolved organic carbon (DOC)，hot water extractable organic carbon(HEOC)，particulate organic carbo(POC)and readily oxidizable organic carbon(ROC)and enzyme activities. The results showed that in 0-20 cm soil layer，DOC，HEOC，POC and ROC contents of S2，S4 and S6 treatments increased by 17.04%-43.71%，5.45%-28.68%，40.94%-83.46% and 8.55%-22.22%，respectively，compared with S0 treatment，and with the increase of desulfurized gypsum application，the labile organic carbon fractions content increased. In the 20-40 cm soil layer，DOC，POC and ROC contents were significantly higher in the S4 and S6 treatments than in the S0 treatment. Carbon pool management index was significantly higher in S2，S4 and S6 treatments than in S0 treatment in both soil horizons. In the 0-20 and 20-40 cm soil layers，compared with S0 treatment，the cellulase，β-glucosidase，polyphenol oxidase and overall enzyme activities were increased by 21.12%-48.60%，37.81%-121.62%，4.73%-44.09%，10.29%-34.56%，11.89%-57.77%，15.98%-93.50%，2.14%-42.62%，5.51%-31.75%，respectively，and the above enzymes activities were significantly increased with the increase of desulfurized gypsum application. The sucrase activity of S2，S4 and S6 treatments was significantly higher than that of the S0 treatment only in the 0-20 cm soil layer. POC and ROC contents were significantly and positively correlated with cellulase，β-glucosidase，polyphenol oxidase and overall enzyme activities in both soil layers. DOC and HEOC were also significantly and positively correlated with cellulase，β-glucosidase，polyphenol oxidase and overall enzyme activity in 0-20 cm. Grey correlation analysis and pathway analysis further indicated that cellulase，β-glucosidase and polyphenol oxidase were the key enzyme affecting soil labile organic carbon fractions. This research indicated that with the increase in the application amount of desulfurized gypsum，the content of soil labile organic carbon fractions and the activity of carbon conversion enzymes in the surface saline soil increased significantly. The activities of cellulase，β-glucosidase，and polyphenol oxidase could significantly influence the content of soil labile organic carbon fractions.