Abstract: In order to explore the law of flower color change of Hibiscus syriacus during the flowering process and the influence of physical and chemical factors such as pH, metal ions and water content on its flower color, the composition and physicochemical factors of anthocyanins in the petals of H. syriacus ‘Qiansiban’ and ‘White Chiffon’ at different blossoming periods were studied respectively by the color chromato-meter, ion emission spectrometer and high performance liquid chromatography-mass spectrometry. The results showed that:（1）In terms of the composition of anthocyanins, 10 kinds of flavonoids such as Quercetin-3-glucoside, Luteolin-7-O-glucoside, and Santolol-7-O-glucoside were detected and identified in the petals of the two varieties, and 5 kinds of anthocyanins such as Mallorin-3-O-glucoside were detected and identified in the H.syriacus ‘Qiansiban’, and no anthocyanins were detected in the H. syriacus ‘White Chiffon’.（2）In the process of blossoming, the brightness of the flower color increased, the color degree decreased, and the color changed from purplish red to lavender, and light yellow to white respectively. During the blossoming, the composition of anthocyanins remained unchanged, and the content of anthocyanins and total anthocyanins gradually decreased in H. syriacus ‘Qiansiban’.（3）The pH of petals in H. syriacus ‘Qiansiban’ and ‘White Chiffon’ were both acidic, and the activities of Peroxidase（POD） and Polyphenol oxidase（PPO） showed significant difference in different periods. Among them, POD activity in H. syriacus ‘Qiansiban’ was higher than that in H. syriacus ‘White Chiffon’, while PPO activity was the opposite; calcium and magnesium ions were the highest content of metal ions in H. syriacus petals, while copper, iron, manganese, zinc and other metal ions had low content in H. syriacus petals.（4）In terms of correlation analysis, during the blossoming of H. syriacus ‘Qiansiban’, the color degree C* was significantly positively correlated with hue a*, and significantly positively correlated with calcium ion, iron ion and manganese ion respectively; during the blossoming of H. syriacus ‘White Chiffon’, the color degree C* was significantly positively correlated with hue b* and PPO activity, and negatively correlated with hue a* respectively. The research showed that the anthocyanins were the material basis of flower color change of H. syriacus flower petals. Besides anthocyanin content, the flower color change process was also closely related to the content of calcium, iron, manganese and other metal ions. PPO activity was a potential biochemical factor to promote the degradation of flavonoids in white flower varieties.