Abstract: In order to understand the difference in cold adaptation and the relationship between leaf structure and cold resistance of diploid,tetraploid and hexaploid of Camellia reticulata,6 populations under low temperature stress were investigated by measuring relative electrical conductivity (REC) and semilethal temperature (LT50) by Logistic Equation.Leaf anatomical structure was observed by paraffin method and scanning electron microscopy.The correlation between physiological indexes (REC & LT50) and anatomical structure indexes was analyzed.The results showed:① LT50 of the populationsof tetraploid (XC,HD) was lower than that of diploid andhexaploid,and LT50 of hexaploid YY was higher than diploid ZY,but lower than YB and SB.The cold resistancedid not show an increasing tendency by ploidy levels,and in the overall view,the tetraploid populations showed greater cold resistance than that of the diploid and hexaploid;② 12 indices of the leaf anatomical structure showed a very significant difference in between the 6 populations.The thickness of upper and lower epidermis(TUE,TLE) was negatively correlated with -4℃—-12℃ REC and LT50,and the stomatal density (SD) was positively correlated.It is concluded that the TUE,TLE and SD could be used as morphological indices to evaluate the cold resistance of populations at different ploidy levels.The results provide theoretical support for the directional breeding of Camellia reticulate.