The issue of desertification and the consequent soil erosion is a prominent global environmental concern, especially in dryland regions. Biological soil crusts (biocrusts) are crucial for enhancing the ability of soil to resist erosion; however, the underlying microbial enzymatic mechanisms are still poorly understood. In this study, samples of biocrusts (cyanobacterial crusts and moss crusts) from the Gurbantunggut Desert were collected to explore the function of carbonic anhydrases (CAs) in enhancing soil shear strength. The findings revealed that biocrust development significantly enhanced soil shear strength, especially in moss crusts. Variations in shear strength were strongly correlated with CA activity and bacterial composition. Biocrust development also significantly enhanced CA activity, demonstrating a positive correlation with shear strength. In line with the changes in shear strength and CA activity, bacterial abundance also increased in biocrusts, with Bacilli and Bacteroidia significantly contributing to CA secretion and promoting soil shear strength. Moreover, three Bacilli strains capable of producing CAs were isolated from biocrusts. Further data from scanning electron microscopy verified that the carbonate crystals induced by these bacterial CAs can effectively bind sand particles, thereby significantly enhancing the shear strength of the sand. In summary, the current study provides robust evidence that supports the role of CAs in enhancing shear strength during biocrust development in dryland ecosystems. These results offer a unique enzymological perspective for understanding the contribution of biocrusts to mitigating soil erosion and highlight the significance of species selection in biocrust restoration and desertification control.