Though leaf mutant cultivars of Cymbidium sinense 'Damo' have a high ornamental and economic value, the mechanism of mutant is still unknown. The photosynthetic pigments content, chlorophyll fluorescence kinetics parameters of 'Green Damo' and four leaf mutants of 'Damo' were compared and analyzed. The content of carotenoid and chlorophyll on the yellow part of the mutant leaves were significantly less than that of the green part respectively. The content of chlorophyll was much lower, leading to the increase of Caro/Chl ratio and leaf yellowing. The determination of chlorophyll fluorescence kinetics parameters showed Fv/Fm and NPQ values on the yellow parts were lower accordingly, while qp and Y(Ⅱ) values were higher, indicating that the result was related to the high ratio of the chlorophyll a and carotenoid. The further observation of chloroplast ultrastructure observation found that the integrity degrees of chloroplast development on the green part of different mutants varied and chloroplast structures were damaged more severely on the yellow part. The result showed Fv/Fm values of green parts went with the integrity degrees of chloroplast development. qp and Y (Ⅱ) values were consistent with content of chlorophyll and carotinoid. However, Fv/Fm, qp and Y(Ⅱ) values on the yellow part did not show such a consistency, indicating that the result may arise from the severely damaged chloroplast structure on the yellow part of the mutant leaves.