According to field experiments in the past two years of a varietyof winter wheat with different sowing dates, the tempering for coldresistence before wintering, the interrupted growth of green leaves during winter and the main symptoms of frost damage are investigated.It is found that the recouping effects of tillering and earing for frost-injured stems may offset the decrease of yield. Based on climatological data, classification of safe and hazardous types, each of which contains 3 substypes is made of overw intering ecological conditions.