Biological soil crusts are widely distributed in the desert as an important biological factor to stabi-lize the sand dunes and promote restoration of sandy ecosystem. Landsat remote sensing images of Mu Us Desert in 1989, 2002 and 2006 were used to extract spatial distribution of biological soil crusts and land de-sertification based on the biological soil crust index and NDVI threshold. Furthermore, the relationship be-tween biological soil crusts and land desertification was discussed. The results show that the areas covered by biological crusts accounted for 54.77%, 55.72% and 64.29% of the total area in the three study years, re-spectively, indicating biological soil crusts in the study area increased continuously. In addition, the connec-tivity among crust patches was enhanced, and the crust stability was further strengthened. In contrast, the degree of land desertification was gradually weakened during the study period, as the composite index of land desertification dropped to 2.65 in 2006 from 3.24 in 1989. Biological soil crusts distributed most widely(over 70%) in the lands experienced moderate and severe desertification. However, the area of biological soil crusts continued to decline in extremely severely desertified lands, accounting for 19. 40%, 5. 76% and 2.80 % of the total area of the extremely severely desertified land in the three study years, respectively. The number of biological soil crusts was increasing in extremely severe desertification land, indicated by the ratio of 19.40%, 33.18% and 45.21% in the three study years, respectively.