Biocrusts play an important role in the ecosystem of arid and semi-arid regions. At present, lots of studies have concerned on the influence of the existence of biocrusts on soil enzyme activity. However, there are few studies focusing on the relationship between basic characteristics of biocrusts and soil enzyme activity. In this study, five types of biocrusts, including shifting sand, algal crust, lichen crust, lichen-moss crust, and moss crust, were studied in the Hongwei natural vegetation zone of the Shapotou Desert Research and Experiment Station of the Chinese Academy of Sciences. The variation patterns of the thickness, chlorophyll a, exopolysaccharide, extracellular protein, and C, N and P contents as the main characteristics of the biocrusts in different compositions of the biocrusts and their effects on soil enzyme activity beneath the crusts layer were investigated. Results showed that:1) thickness and contents of chlorophyll a, exopolysaccharide, extracellular protein, C, N, and P, and C/N, C/P, and N/P from algal crust to moss crust ranged from 2.28-8.29 mm, 1.79-8.05 μg/cm, 14.60-20.43 mg/kg, 13.16-19.37 mg/kg, 5.54-51.42 g/kg, 0.44-3.36 g/kg, 0.23-0.54 g/kg, 9.62-15.32, 24.07-94.98, and 1.92-6.23, respectively. Meanwhile, the above-mentioned crusts characteristics were significantly increased in different compositions of biocrusts (P<0.001), while exopolysaccharide and extracellular protein did not have significant differences among lichen crust, lichen-moss crust, and moss crust (P>0.05); 2) C, N and P contents and their stoichiometric characteristics increased significantly in different compositions of biocrusts, while C and N had a larger coefficient of variation compared to P. N/P in different compositions of biocrusts was less than 14, indicating that different compositions of biocrusts are more easily restricted by N; 3) The soil enzyme activity beneath crusts showed significant differences in different compositions of biocrusts and characteristics of biocrusts were positively correlated with soil enzyme activity. Soil invertase, urease, alkaline phosphatase and protease activity beneath algal crust, lichen crust, lichen-moss crust and moss crust were significantly different between 0-5 cm and 5-10 cm (P<0.05). With the increasing of soil depth, soil enzyme activity decreased. The two-factor analysis of variance showed that the interaction of different composition of biocrusts and soil depth had significant effects on the activity of catalase, invertase, urease, alkaline phosphatase and protease (P<0.01); 4) All of the above crusts characteristics had significant influence on soil enzyme activity. The individual effects in the redundancy analysis showed that the importance of the biocrusts characteristics on soil enzyme activity beneath the crusts was as follows:extracellular protein > exopolysaccharide > C/N > P > C/P > N/P > chlorophyll a > N > crust thickness > C, explaining the variation of enzyme activity by 92.2%, 90%, 75%, 68.9%, 62.8%, 62.3%, 59.6%, 57%, 56.8%, 52.1%, respectively. However, the conditional effects analysis showed that extracellular protein, C/N and P in biocrusts were the main influencing factors on soil enzyme activity with the explanation of 92.2%, 4% and 2.2%, respectively. The results of the study will help to further clarify the contribution of different composition of biocrusts to soil enzyme activity and will enrich the understanding of biocrusts for its ecological importance in the restoration of desert soil and the improvement of soil fertility.