The loess flow is the result that the variation of the moiture of the loess makes the exogenic force of the loess to vary. It has a limited slope angle. When the slope angle of the loess is more than the limited one,the loess flow is occuredo The configuration of surface and cover of vegetation have influence on the frequency and intensity of the loess flow.The loess flow of the concave slope is occurred easier than that of the straight one which is easier than that conver one; when there is not vegetation the intensity of the loess flow is more than that when there is vegetation under other conditions are same.