Abstract: The resonance light scattering (RLS) spectral characteristics of the interaction between rose Bengal and mexiletine hydrochloride in the presence of cetylpyridinium bromide were investigated. A dual-wavelength resonance light scattering (DWO-RLS) method for the determination of mexiletine hydrochloride in drugs was established. In a weakly acidic solution, rose Bengal interacts with mexiletine hydrochloride and cetylpyridinium bromide to form a red ternary ion association complex, which led to a significantly enhanced resonance light scattering signal and produced two strong characteristic scattering peaks at 372 nm and 596 nm. In these two wavelengths the mass concentration of mexiletine hydrochloride was in the range of 0.004 to 0.65 mg·L^-1 and had a good linear relationship with the resonance light scattering enhancement intensity (ΔI_RLS), with detection limits of 0.003 2 mg·L^-1 (372 nm) and 0.003 8 mg·L^-1 (596 nm), respectively. When measured by the dual-wavelength resonance light scattering (DWO-RLS) technique, the detection limit was lower, only 0.001 8 mg·L^-1. When the DWO-RLS method was applied to the determination of mexiletine hydrochloride in commercially available mexiletine hydrochloride tablets, and the recovery was 98.5%-103%, and the relative standard deviation was 2.0%-2.7%.