Abstract: It was reported that in a solution of pH 1.0,through the charge transfer reaction,a stable coordination complex with mole ratio of 1 to 1 was formed between erthromycin and methyl violet,by heating at 50 ℃ for 10 min in a water bath.The absorption maxima of the complex was found at the wavelength of 583 nm,where the molar absorptivity of 1.61×104L·mol-1·cm-1 was obtained.Beer′s law was kept up to the concentration of 2.10 mg of erythromycin per 25 mL of solution.Precision was tested at the concentration level of 0.52 mg/25 mL,and the value of RSD (n=9) obtained was 0.91%.Detection limit (S/N=3) of the method was found to be 1.51 mg·L-1.Recovery test was made by standard addition method,values obtained were ≥97.5%.