In this study, we selected four typical communities: Caragana korshinskii，Artemisia ordosica，Stipa breviflora and Agropyron mongolicum in desert steppe of Ningxia as the research objection, by analyzing the distribution characteristics of soil LOC fractions: microbial biomass carbon (MBC), dissolved organic carbon (DOC), and easy oxidation organic carbon (EOC) at different soil depths (0-5, 5-10 and 10-15 cm) in different community types ,in order to probe into the relationship between soil LOC fractions and soil enzyme (invertase, urease, alkaline phosphatase and catalase) activities. Results show that: (1) the soil SOC and MBC, EOC content in four typical communities declined with the increasing of soil depth, which in surface layer (0-5 cm) were significantly(P<0.05) higher than that in deep soil(5-10 and 10-15 cm), whereas DOC content increased fristly and then decreased with the increasing of soil depth. In the same depth, the soil LOC fractions in shrub (C. korshinskii and A. ordosica) were higher than that in herbs (S. breviflora and A. mongolicum); (2) The soil enzymes (invertase, urease, alkaline phosphatase and catalase) of four typical communities generally showed a declined trend with the increasing of soil depth, fluctuate appeared at local depth of soil, but at same layer, the soil enzyme activities did not presented the same distributioncharacter in different community types. (3) The soil LOC fractions of four typical communities except for DOC, other indicators were showed significant (P<0.05) correlation with SOC, and has a certain correlation with soil enzyme activities, microbial biomass entropy and organic carbon activity, which indicated that soil LOC fractions not only depend on the total organic carbon(TOC), but also closely related to soil enzyme activities.