Abstract: In this study, we detected the physiological differences of male and female plants of Salix viminalis in electrical conductivity (EC), superoxide (O·-2) production rate, contents of osmotic adjustment substances and activities of antioxidant enzymes at 40 ℃/30 ℃(day temperature/night temperature), and analyzed the variable coefficient (VC) and differentiation coefficient (VST) of all physiological traits. The aim of this study was to provide reference for variety breeding and introduction. Under high temperature stress, EC value and O·-2 production rate increased significantly, but they were significantly higher in female plants than in male plants. Proline (Pro) and solute protein (SP) contents rose significantly, but the two contents in male plants were significantly higher than in female plants. The activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (AsA-POD) went up significantly, the activity of peroxidase (POD) declined markedly, but the activities of the four enzymes in male plants were significantly higher than those in female plants. Similar VC values of all physiological traits in both sexes indicated that the variation of all physiological traits for male and female plants were consistent. The mean VST of all physiological traits (VST =17.06%) indicated that the variation between male and female plants was smaller than that within male and female plants (clones). In general, abundant physiological variations under high temperature stress exist in clones of Salix viminalis, yet male plants possess more strongly regulated and adaptive ability. Thus, to obtain heat-resistance germplasm, male Salix viminalis plants should be selected in future breeding project.