This research shows: Varieties of winter wheat are infected by wheat yellow stripe rust, the equation is y= 0.3646x about disease index of 3 leaves on the top(x) and losing rate(y) of wheat yield; the fit period for preventing yellow stripe rust by using medicaments is from the beginning of leaves to the beginning of heading. During this period. when disease index of top 3 leaves is up to 3%, it is called preventive target. At this time, applying drugs for only one time can get significant preventive effect.