Abstract: Based on the observed experimental data of winter wheat and climate data of 23 agro-meteorological stations in Hebei province from 1981 to 2007,the variation and trend of winter wheat freezing injury under global warming was analyzed by statistic method.The results showed that the average temperature in winter and the minimum temperature during winter wheat overwinter time had increased significantly.There was no significant downtrend for the range of temperature dropping process when minimum temperature occurred.The negative accumulated temperature decreased obviously during the over-wintering period.The frequency of freezing injury decreased gradually after 1986,and no freezing injury occurred during 1995-2000.Freezing injury came back again from 2000,and acted as extensive temperature reducing at early winter and thawing-freezing damage.The main reasons of frequency rising in freezing injury were as follows,the uncertainty of climate change,abrupt variation of temperature,introducing of weaker winter wheat variety,acclimation shortening of cold resistance,weakening of its intensity,and unsuitable culture measures.Therefore,the prevention of winter wheat freezing injury should take more attention even under climate warming.

Key words: Climate warming, Climate warming, Winter wheat, Freezing injury, Hebei province, Winter wheat planting region