Abstract: To observe the relationship of main carotenoid contents with different petal colors during the petal developmente in Brassica napus L..The petal development was divided into 5 stages in this research. At each stage the contents of total carotenoids，Xanthophyll，lycopene and β-carotene in petals were analyzed by spectrophotometry and HPLC . The results show that：the change of total carotenoid content is consistent with the change of petal color during petal development，which shows that the changes of petal color during petal development is closely related to the total carotenoid content. And the carotenoid contents in different color petals were different. The carotenoid content in yellow petals was the highest，and the carotenoid content in white petals was the lowest. The contents of xanthophyll and β-carotene were decreasing during the petal development，which were consistent with the total carotenoid content. The content of lycopene experienced an obviously change of firstly increasing and then decreasing. Among different color petals，the content difference of lycopene was the largest，which was highest in yellow petals and lowest in white petals. So initially speculate that the total carotenoids play an important role in the formation of petal colors，and in which lycopene may be the major factor.