In neutral medium,pyrogallol red-copper(Ⅱ) reacts with protein to form a complex.The color of solutions darkened obviously.At 20℃,the reaction reaches balance after 10min.The mole ratio of pyrogallol red and copper is 5∶ 2.At the largest absorb wavelength of 549nm,the darkening intensity is proportional to the concentration of protein.The recovery of the method is 93.1%~108.5%,the regression equation is δA=0.010C-0.0255 and R2=0.990 3.The inspection on many types of milk using this method leads to satisfying results.