Abstract: Mechanism of the interaction between the reagent zincon and bovine serum albumin (BSA) was studied by spectrophotometry in visible spectral region with variation of concentration of BSA.Based on the spectral change of the reaction system at pH 4.2,with decrease of absorbance at 465 nm (λmax of zincon) and increase of absorbance at 2 new peak wavelengths of 564 nm and 600 nm with increase of concentration of BSA,it was concluded that a compound complex was formed between the 2 reactants.It was explicated that both the electrostatic effect and hydrophobic effect played important role in the formation of the zincon-BSA compound complex,with the latter as leading role.It was further proved by the reaction between zincon and BSA in comparison with chitosan of different concentrations.Some other influential factors of the reaction were also tested and results given.