Abstract: Taking the mature leaves of Chinese endemic species Lagerstroemia intermedia and exotic species Lagerstroemia speciosa as test materials, the leaf length（L）,leaf width（W）,leaf perimeter（LW） and leaf area（LA） of sample leaves were measured by image processing method, and the single leaf area of the two species was fitted by different types of linear or nonlinear regression equations.The leaf morphological characteristics and estimation model of single leaf area of L.intermedia and L.speciosa were studied, in order to provide reference for ecological function evaluation of tree species.The results showed that there were significant differences in leaf length（L）,leaf width（W）,leaf perimeter（LW） and leaf area（LA） between L.intermedia and L.speciosa.The univariate regression model with the highest fitting degree of single leaf area of L.intermedia was LA=4.254+0.305LW+0.051LW~2 and LA=6.200+0.063LW~2（R~2=0.932）,and the multivariate regression model was LA=0.547 l+0.449W（R~2=0.884）.The univariate regression model with the highest fitting degree of single leaf area of L.speciosa LA=2.261×W^1.898（R~2=0.834）,and the multivariable regression model was LA=0.204L+0.371W+0.442LW（R~2=0.907）.It could be seen that the leaf morphological characteristics of L.intermedia and L.speciosa were different, and the leaf morphological characteristics in the same tree species were also different.The single leaf area of L.intermedia and L.speciosa could be estimated by the univariate or multivariate regression model with the highest fitting degree.