In this paper, a sensitive resonance light scattering (RLS) method for the determination of protein is reported. In the Tris-HCl (pH 7.50) buffer, protein enhanced the RLS intensity of the Y(3+)-2-thenoyltrifluoroacetone (TTA)-sodium dodecyl sulphate (SLS) system. The enhanced RLS intensities were in proportion to the concentrations of proteins in the range 8.0 x 10(-9)-1.0 x 10(-5) g/mL for BSA, 1.0 x 10(-8)-1.0 x 10(-5) g/mL for HSA and 1.0 x 10(-8)-1.0 x 10(-6 )g/mL for EA, and their detection limits were 5.0, 5.4 and 6.7 ng/mL, respectively. Actual samples were satisfactorily determined. The interaction mechanism was also studied.