In the Yellow River Delta, nearly 50 percent of soils are saline and alkaline. Soil salinization can suppress microbial activity and thus affect the decomposition and transformation of soil organic carbon, while little information was found about the effects of salinity and exogenous C and N amendment on the decomposition and transformation of soil organic carbon in this area. A laboratory experiment was conducted to investigate the effects of soil salinity and exogenous substances on the turnover of organic carbon under conditions with 25℃ and 60% water holding capacity over 45 days. Three levels of salinity (S1: 0.1%; S2: 0.5%; S3: 0.9%) using NaCl (w/w) were imposed in the saline-alkaline cultivated soil in Yellow River Delta. Soil was amended with or without C (750 mg/kg) or inorganic N (30 mg/kg) as glucose or NH₄Cl, and 4 treatments were established, including (Control: no substrates addition, N: NH₄Cl addition, C: glucose addition, C+N: glucose and NH₄Cl addition). The CO₂-C emission, soil microbial biomass carbon (SMBC), dissolved organic carbon (DOC) and calculation of the respiratory quotient(qCO₂)were determined. Without glucose addition, the cumulative amount of CO₂-C emission was highest in S1 during the incubation, and it was decreased by 18.3%-23.7% and 24.3%-39.8% in S2 and S3 compared with S1, respectively. After glucose addition, the cumulative amount of CO₂-C emission little changed among the three salinity soils, and especially it was no significant difference between the three salinity soils in C+N treatment. SMBC was higher in S1 and S2 than that in S3 under the four treatments with substrates addition. Addition of NH₄Cl had no significant effect, but addition of glucose significantly increased SMBC, and SMBC increased by 80.4%-80.5% or 58.0%-58.7% in S1 and S2 in C or C+N treatment, and only 68.9% or 49.7% in S3. The qCO₂ was significant higher in S1 than that in S2 and S3, and it was significantly improved with glucose addition. Compare with the control, DOC reminded unchanged in the N treatment, but it increased in S3 with glucose addition. It was suggested that the CO₂ emission could be depressed with the increase of soil salinity without C addition, and soil salinity had little influence on CO₂ emission after C addition. Microorganism was more sensitive to exogenous carbon and soil salinity. The size and the activity of microbial biomass would be improved with C addition, but higher salinity (>0.5%) could depress the microbial activity and the utilization of exogenous carbon, resulting in higher SMBC and qCO₂ and lower DOC in higher salinity soil.