Abstract: Biological soil crusts (BSCs) are widely distributed in Artemisia ordosica community in Mu Us Desert, northwestern China. They have been proved to play vital hydrological and ecological roles in desert ecosystems. However, the influence of BSCs on soil hydrological processes remains uncertain and controversial. In this study, we conducted a field experiment with two treatments (undisturbed and removed) for two biological soil crusts (lichen crusts and moss crusts) in A. ordosica community in the Mu Us Desert. We compared soil infiltration, evaporation and soil water volume in crust-covered and crust-removed soil. The initial infiltration rate, stable infiltration rate and cumulative infiltration significantly increased under crust-removed treatment (P < 0.05), suggesting that lichen and moss crusts had inhibitory effects on soil water infiltration. The effect of BSCs on soil evaporation was related to the type of BSCs and the evaporation stage. The lichen crusts had no effect on daily soil evaporation and total soil evaporation(P>0.05).The influence of moss crusts on total soil evaporation was similar to that of lichen crusts. The moss crusts inhibited daily soil evaporation in early soil evaporation stage (1-5th day), and promoted it in the late stage (6-15th day). Generally, the soil moisture above 40cm depth under crust-covered soil was higher than that in crust-removed soil, but opposite in moss soil. The soil moisture at each layer above 40cm depth in crust-covered soil was higher than that in crust-removed soil. Compared with the crust-removed soil, soil moisture in crust soil was higher at 5 and 10cm, but lower at 20 and 40cm. The results indicated that lichen crusts should be reserved with no disturbance. Whether the moss crusts should be reserved or disturbed need further discussion. Our results highlight the different hydrological roles of lichen and moss crusts and provide important implications for the management of soil water resource in semiarid areas of northwestern China.