Objective: To investigate the mechanism of quercetin (Que)， baicalin (Bai)， fisetin (Fis) and bovine serum albumin (BSA) forming BSA mono-， di-， tri ligand complexes. Method: The formation mechanism of BSA flavonoid complexes was investigated using UV visible absorption spectroscopy， fluorescence spectroscopy， Fourier transform infrared spectroscopy， Raman spectroscopy， and other methods； The changes in thermal stability of BSA were studied using DSC； The changes in crystallinity and solubility of flavonoids after binding BSA were investigated using XRD； Observe the morphology of BSA flavonoid complex by scanning electron microscopy； Exploring the dynamic binding of flavonoids and BSA through molecular dynamics simulation. Result: The hydrophobicity of the BSA aromatic amino acid residue microenvironment gradually increased with the increase of flavonoid content； During the formation of BSA triple ligand complexes， the content of alpha helices gradually decreases， ultimately reaching only 20.90% ± 0.019 and 30.07% ± 0.008， respectively； BSA single and triple ligands have a stabilizing effect on the conformation of BSA， and the g-g-g content of BSA can be increased from 62.04% ± 0.023 to 77.30% ± 0.028. BSA dual ligands as a whole have a negative effect on the conformation stability of BSA； The addition of flavonoids reduces the thermal stability of BSA， with BSA triple ligand showing the worst thermal stability. The thermal denaturation temperature of BSA decreases from (145.63 ± 6.2) ℃ to (132.19 ± 5.4) ℃； Flavonoids are in an amorphous state in BSA， and their crystallinity decreases. As the number of ligands increases， the solubility of flavonoids is further improved； The increase in the amount of flavonoids disrupts the smooth surface of BSA， making it loose， and even the BSA triple ligand exhibits a scale like crystal structure； The binding process between flavonoids and BSA is relatively stable， and the stability of BSA is enhanced， with BSA triple ligand having the best stability. Conclusion: Que， Bai， and Fis， when acting alone or co loaded onto BSA， will affect each other's structure and properties. The degree of influence varies depending on the number of ligands.