Objective:To develop a novel method for the determination of trace malachite green (MG) in samples. Methods: In the H2 SO4 medium, MG reacted with phosphomolybdic acid (PMA) to form an ion - associate. The resonance rayleigh scattering (RRS) intensities of the ion -associate enhanced with the MG increasing. Based on those, RRS was proposed for the determination of trace MG. Results:The intensity of RRS was directly proportional to the mass concentration of MG in the range of 0. 18 - 5. 0 μg/ml, and the detection limit was 55 ng/ml. Th...