Abstract: Based on the investigation data of six main types of saline-alkali soil in Xinjiang of Northwest China, this paper analyzed the spatial distribution patterns of organic carbon (OC) and microbial biomass carbon (MBC) in these soils, and explored the relationships between the soil OC and MBC and environmental factors. The OC content in the soils was in the order of pure soda (CSD) > chloride-sulfate (L-LS) > sulfate-chloride (LS-L) > soda (SD) > sulfate (LS) > chloride (L), and significant difference (P< 0.05) was observed among the different types of saline-alkali soil, with the exception between LS and SD, and between SD and LS-L. The OC content in the soils decreased with depth, and had obvious stratification characteristics. Similarly, the MBC in the soils was in the order of CSD > LS > L-LS > SD > LS-L > L, and significant difference (P < 0.05) was existed among the different types of saline-alkali soil, with the exception between L-LS and SD. The MBC in the soils had a great difference, and was not in accordance with the OC content, which could be explained by the differences in the habitat and feeding pattern of soil microbes. In a given soil type, MBC also had obvious stratification characteristics. The MBC decreased sharply with soil depth, and the decrement varied with soil types. Not as previously reported, the soil MBC in this study had no linear relationships with soil moisture content and soil bulk density