Abstract: Weather conditions of dry-hot wind were simulated by artificial control to compare the effects of heavy and light degree of dry-hot wind on winter wheat physiology in field at early and middle grain filling stages. The results showed that the dry-hot wind at middle stage of grain filling had more negative effects than at early stage of grain filling, and the heavygrade dry-hot wind harmed more than the lightgrade one. On the 2nd day after heavy dry-hot wind occurred at middle stage of grain filling, the photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (C_o) of flag leaf decreased by 19.4% to 36.6%, 44.1% to 58.0%, and 24.3% to 41.7%, respectively. For light dryhot wind, the above index decreased by 9.7% to 20.2%, 28.2% to 34.0%, and 19.9% to 31.8%, respectively. The decreased percentage of SPAD and root flux activity (G_n) also reached the maximum with the heavygrade dry-hot wind at middle stage of grain filling. There was no obvious stressed effect on winter wheat for lightgrade dry-hot wind at early stage of grain filling. At early stage of grain filling, P_n and SPAD of flag leaf could repair to a certain extent after dryhot wind weather, but the damaged physiological indexes could not be repaired when the dryhot wind occurred at other stages. Under the condition of C_o >0.1 mmol·m^-2·s^-1, the stressed effects on T_r were more than on P_n.

Key words: atmospheric visibility, PM₂₅ and PM₁₀, PROVSV curve analysis, relative humidity (RH)