Abstract: Loropetalum chinense Olive var. rubrum Yieh has been widely used in beautify cities and roads because of its red leaves，but its red leaves could turn green during summer time. The structure，the contents of chlorophylls，carotenoid and anthocyanin of red leaves and green leaves were studied in this papers. The results showed that after turning green：（1）Thickness of the leaves became weaker，and the cell size of epidermis and mesophyll became smaller；（2）Stomata index and stomata density declined distinctly；（3）Size and amount of chloroplasts in every mesophyll cell shrinked，but the contents of chlorophylls and carotenoid of leaves increased；（4）The contents of anthocyanin remarkably declined. According to these results and former reports，high temperature was possibly the key factor for green turning in summer time.

Key words: Loropetalum chinense var. rubrum, structure of leaf, chlorophyll, anthocyanin