Seven oneyearold white poplar hybrid clones were selected as the experimental materials and the cold resistance characters had been comprehensively assessed according to the analysis of the water parameters (Ψ0π,Ψ１００π,RWC0,ROWC0 and εmax)by P-V technology before leaf abscission in autumn and the dynamic changes of relative conductivity,potassium leakage rate,SOD and POD activities in winter.The results showed that there was a certain changing pattern existed in the physiological indexes of the clones.Relative conductivity and potassium leakage rate had decreased to the minimum in December,then gradually increased and the largest variation in clones was in February.The activities of SOD and POD had significant difference in different periods among clones.Therefore,the cold resistances gradually increased from the beginning of defoliation and achieved its maximum in December and January of the next year and then decreased rapidly in February.The difference of cold resistances among the clones was the maximum in February.The data revealed that the most of water parameters and the cold resistances index had different correlation degree in different periods of winter.The correlation was most evident in spring,in which the Ψ0π was a most significantlyed index while Ψ100π was not .