A new resonance scattering spectral (RSS) method for the determination of human serum album (HSA) has been proposed with the resonance scattering enhanced reagent of K 3[Fe-(CN) 6]. In the medium of HCl (2.0×10 -3 mol/L), HSA may combine with 3- by intermolecular forces (mainly by electrostatic force) to form { 3- n-HSA m+} k nanoparticle of the ion-association complexes of HSA m+- 3- n. There is a strongest resonance scattering intensity at 351 nm, owing to the existence of the resonance scattering of the nanoparticle, 3- molecular absorption and the non-distribution of the emission intensity of Xe lamp in the range of 200-1000 nm. In addition, two resonance scattering peaks at 470 and 700 nm were observed. The HSA concentration in the range of 0-12 μg/mL is linear to the resonance scattering intensity at 351 nm. The determination limit of this method is 0.1 μg/mL HSA, about ten-fold lower than that of Coomassie brilliant blue protein assay. This method has been used for the determination of HSA in human serum and synthetic samples with satisfactory results. The mechanism of enhanced resonance scattering light, the TEM of the particle, the concepts of quasi-elastic absorption and un-elastic absorption were also discussed. In the medium of HCl (2.0 × 10⁻³), a new resonance scattering spectral (RSS) method for the determination of human serum album (HSA) has been proposed with the resonance scattering enhanced reagent of K 3 [Fe- (CN) 3 mol / L), HSA may combine with 3- by intermolecular forces (mainly by electrostatic force) to form {3- n-HSA m +} k nanoparticle of the ion-association complexes of HSA m + -3- n. There is a strongest resonance scattering intensity at 351 nm, due to the existence of the resonance scattering of the nanoparticle, 3-molecular absorption and the non-distribution of the emission intensity of Xe lamp in the range of 200-1000 nm. The HSA concentration in the range of 0-12 μg / mL is linear to the resonance scattering intensity at 351 nm. The determination limit of this method is 0.1 μg / mL HSA, about ten- fold lower than that of Coomassie brilliant blue protein assay. This meth od has been used for the determination of HSA in human serum and synthetic samples with satisfactory results. The mechanism of enhanced resonance scattering light, the TEM of the particle, the concepts of quasi-elastic absorption and un-elastic absorption were also discussed.