Oases in Hexi Corridor was taken as examples for studying the forest coverage of oases in arid sandy area. Results are as follows: ①The oasis forest coverage(F) is mainly determined by the maximum wind velocity(Vmax) and the effective protection distance(L) of key shelterbelt. Also, the effective protection distance of key shelterbelt is controlled by the average height and the protection coefficient of shelterbelt. ②The ratio of V/L has consistency regularity same as distribution of F. Different ratio represents the forest coverage with the optimal protection benefit to reduce above 20% of the maximum wind velocity under different heights of key shelterbelt, based on which a no-linear ecological mode of oasis forest coverage in arid sandy area has been established. ③The model has passed the test of forecasting adaptability by using the data of forest coverage from 1979 to 1994 in a new constructed protective forest system on northeast rim of WulanBuh Desert, which proved that it is possible to apply this mode in actual application.