We analyzed the anthocyanin profiles in 8 cultivars of Rieger begonia, including red, redwhite, pink, rose red, yellow, yellowred, pinkwhite, white. The petal phenotype was observed according to Visual inspection, Royal Horticultural Society Color Card (RHSCC) and Colorimeter (CR400). The microstructure and distribution of pigment cell was observed by the tissue section method. Dualbeam UVvisible spectrophotometer and HPLCESIMS were used to measure and analyze the anthocyanin composition in petals. Its hoped to provide references for further studying of the colouration mechanism and color breeding of Rieger begonia. The results showed that: (1) the L^* value of Rieger begonia petals decreased as the color became darker, while the a^* value showed the opposite trend. The a^* and C^* value were significantly negatively correlated with L^* value, and were the main factors affecting L^*. (2) The petal pigments of red varieties were mainly distributed in the upper epidermal cells and sponge tissue. The petal pigments of redwhite varieties were mainly distributed in the upper and lower epidermis, and the accumulation of the lower epidermis was greater. The petal pigments of pink and rosered varieties were mainly distributed in the upper and lower epidermal cells. A small amount of pigment was contained in the epidermis of yellowpink petals, while the yellow and white varieties had almost no pigment accumulation in the petals. The upper epidermal cells of Rieger begonia petals were all conical, the red and redwhite varieties had the highest conization. The lower epidermal cells of the petals were flat rectangles. (3) A total of 15 anthocyanins were detected in the petals of 8 cultivars of Rieger begonia, of which 10 were peonidin, 3 were cyanidin, 1 was malvidin, and 1 was delphinidin, with the majority of acylated anthocyanins. The total anthocyanins in petals of red varieties was the highest, followed by rosered varieties, while no anthocyanins in yellow and white petals. Except for pink flowers, other anthocyaninscontaining varieties had the highest content of peonidin, accounting for more than 50% of total anthocyanin. Its the main coloring substances in the petals. (4) Total anthocyanins in petals of Rieger begonia was positively correlated with a^* and C^* values, and negatively correlated with its L^* value. The study shows, anthocyanins accumulation is beneficial to the redness of Rieger begonia petals, and affects the C^* and L^*. The number of pigmentdistributed cells and the upper epidermal cell conization significantly affect the petal coloration and the main coloring substance of the petal is peonidin and acylation which may affect the brightness of the petal.