The rupture of a microbiotic crust under the impactof a single saltating grain was theoretically studied using the classical theoriesof elastic thin plate and plastic mechanics. A quantitative relation between thecritical impact velocity of saltating grain and the characteristics of microbioticcrust was obtained. The effects of microorganisms were taken into account throughthe values of Young's modulus, Possion ratio and the yield stress of microbiotic crust,which are mainly determined by component species, numbers, and development stagesetc. The current study indicates that a rigid and weak microbiotic crust ismore easily broken down by saltating grains than a soft and strong one. The formulawe obtained will be helpful to evaluate the relationship between the microbiotic crustand the motions of wind-driven grains.