A novel and sensitive immunonanogold resonance scattering (RS) spectral probe was obtained for rapid detection of microalbumin (Malb), using 10 nm gold nanaoparticle to label goat anti-human Malb. It was based on that the gold-labeled anti-Malb took place nonspecific aggregation and exhibited a strong RS peak at 577 nm in pH 5.2 C(6)H(8)O(7)-Na(2)HPO(4) buffer solution containing polyethylene glycol (PEG), and the immunocomplex formed after specific reaction of gold-labeled anti-Malb with Malb, which led to a decrease in the intensity of RS peak at 577 nm considerably. The decreased RS intensity at 577 nm (DeltaI (577nm)) was linear to the concentration of Malb in the range of 4-128 ng/mL, with a detection limit of 3.2 ng/mL. The proposed method was applied to detect Malb in healthy human urine samples with satisfactory results.