The molecular structure of betacyanin is susceptible to degradation and fading due to adverse environmental effects. Therefore, the development of natural color fixatives has become a research hotspot in the industry. It has been proved that Sophora japonica L. has a color protection effect on a variety of natural pigments. In order to clarify the mechanism of Sophora japonica L. extract on the stability of betacyanin, the protective effect of 0.5 wt.% Sophora japonica L. extract under different environmental conditions was systematically explored. Moreover, molecular docking was conducted to simulate the binding mode.he results showed that the retention rate of pigment increased by 29.97% after heating at 90 °C for 5 h. After continuous illumination for 14 days, the pigment retention rate could reach 52%. Betacyanin had the best stability at pH 3.0-4.0; Al³? seriously damaged the structure of the pigment, and the retention rate increased by 15% after adding the extract, and the antioxidant capacity was significantly enhanced. The binding of rutin and quercetin to betacyanin was mainly through hydrogen bonding. This study showed that 0.5 wt.% sophora japonica extract could significantly reduce the degradation of betacyanin, and hydrogen bond was the main mode of action. In addition, it provides theoretical support for the application of sophora japonica extract as a natural color stabilizer for betacyanin.