Abstract: It was found that in a buffer solution of pH 7.0,an electrostatic association compound was formed between human serum albumin (HSA) and acridine orange (AO),leading to a remarkable enhancement of the intensity of resonance scattering spectra measured at 362 nm.Linear relationship between the values of ΔI (Δ=I-I0,where I0 is the intensity of the spectral peak without adding HSA) and values of concentration of HSA was obtained in the range of 0 to 1.3 mg·L-1 of HSA,with a detection limit of 32 μg·L-1.The above reaction conditions were used in the determination of HSA.