Abstract: Three cultivars of sweet Osmanthus,including O.fragrans ’Ruanye Dangui’,’Liuye Yingui’ and ’Sijigui’ were conducted to study the changes of pigment,soluble sugar and protein of petals of different cultivars during the period of their florescence and senescence.The results showed as follows:(1)It is the same with these three different cultivars that during the whole florescence period from the initial stage to the middle stage,then to the late stage,the content of carotenoid and anthocyanidin experienced an obvious change of firstly increasing and then decreasing,which is consistent with the change of the color of the petal,showing that the changes of the color of the petal during the florescence were mainly caused by the change of the pigment.(2)The content of water,soluble sugar and soluble protein in the petals of these three cultivars decreased obviously during their florescence and senescence,and the decreasing of those in ’Ruanye Dangui’,which had a longer anthesis was slower than the other two cultivars,while the decreasing between ’Liuye Yingui’ and ’Sijigui’ was not significantly different.