Crust is a compact soil layer which distributes widely in arid and semi arid region to resist wind erosion. In this paper the model of crust destruction in wind erosion is suggested to study the crust destruction mechanics, and crust life length is forecasted. Dimensional analysis is applied to establish the constitutive equation of crust wind erosion volume with sand continuous impacting. The numerical calculation results show that crust life length is effected obviously by sand impacting velocity，sand rotational angular velocity，sand impacting angle，sand diameter,dust-storms datasets and its duration. Through statistic analysis and calculation with above influencing factors, the crust life length is 3~8 years and 5.3 years average when the crust thickness is 20 mm. This research can make people more deeply understand natural destruction features of crust, which has important theoretical significance and practical application value in sand-protecting and sandbinding.