Abstract: A purple-red complex could be formed rapidly between azocarmine G and proteins in acidic medium.The absorbance of this complex at its maximum absorption wavelength of 570 nm increased linearly with the concentration of bovine serum albumin(BSA),human serum albumin(HSA) and human Immunoglobulin G(IgG) at least in 15.0 μg/mL.Proteinase and the majority of other coexist substances did not interfere in the determination of protein by the new spectrophotometric method established according to this binding reaction between azocarmine G and proteins.The results obtained by this method,which was simple,rapid,selective and of wide determination range were agreed well with that obtained by Coomassie brillant blue G-250 method.