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Microcoleus vaginatus Gom., the dominant cyanobacterial species in biological soil crusts (BSCs), plays a critical role in forming BSCs. Four inoculum dosages of M. vaginatus (0.5, 1, 3, and 7g center dot m(2)) were inoculated across a sand surface and subjected to five moisture treatments (0, 1, 2, 3, and 4L center dot m(2)). Microalgal biomass, microbial biomass, and enzyme activities (invertase, alkaline phosphatase, and urease) were subsequently determined. In general, microalgal biomass, microbial biomass composed of carbon and nitrogen, as well as alkaline phosphatase and urease activity were increased by increasing inoculum dosages and moisture, whereas invertase activity decreased with higher moisture content. Combination of 7gm(2) inoculum and 2 or 3Lm(2) moisture was recommended for M. vaginatus to recover BSCs. Significant positive correlations were observed between microalgal biomass, microbial biomass, C:N ratios, and enzyme activities. Increasing microalgal biomass can act as an energy source for microbial activity, while the growth of cyanobacteria and microorganisms provides substrates for enzymatic activities. Results from the present study allows better understanding of the conditions for M. vaginatus forming BSCs and offers guidance for successful recovery of BSCs in the field.