Stress susceptibility index (1-Yd/Yp) / (1-∑Yd/∑Yp) used to determine drought resistance on the field is the alter form of drought resistance coefficient (Yd/Yp) . The correlative coefficient above both is r= -1. Therefore, the former doesn't improve the defect of the latter. Using thirty winter wheat varieties as trial materials, after two years experiments, the concept of drought resistance index in crops was put forward, its expressing equation is. the yield in dryland × drought resistance coefficient / ...