Abstract: In aqueous media, clarithromycin and acid chromium K undergoes n-π electron transfer to form a 1:1 type complex with the maximum absorption at 610 nm. Based on this, A method for the determination of clarithromycin by spectrophotometry was established. The sample was crushed and then dissolved with ethanol. 4.00 mL of 1.0×10^-3mol·L^-1 acidic chromic K solution and 1.00 mL of sample solution were added into a colorimetric tube of 25 mL. The volume of the mixed solution was made up to 25 mL with water. After being shaked well, the solution was placed at room temperature for 10 min, and then the absorbance at λ=610 nm was measured using a 1 cm cuvette with the reagent blank as a reference. The absorbence and the mass concentration of clarithromycin in the range of 2.0-100 mg·L^-1 obeyed Beer's law, with the detection limit (3s/k) of 1.2 mg·L^-1 and the apparent molar absorptivity of 6.956×10³L·mol^-1·cm^-1. The method was applied to the analysis of commercially available clarithromycin tablets, giving determined values consistent with the indicated values. Values of recovery obtained by standard addition method were in the range of 96.0%-104%, and RSDs (n=5) in the range of 1.3%-2.1%.