Abstract: OBJECTIVE To optimize the chromatographic conditions for detecting related substances of Matrine and Sodium Chloride Injection by using central composite design-response surface method. METHODS The pH of the mobile phase, the proportion of acetonitrile in the mobile phase and the column temperature were taken as investigation factors, and the retention time, resolution and the number of theoretical plates served as inspection indexes. The study carried out standard normalization and multiple linear regression, and used response surface method to obtain optimal chromatographic conditions. The methodology was verified. RESULTS The optimal chromatographic conditions were determined, the mobile phase was 0.2% triethylamine aqueous solution(adjusted pH to 6.5 with phosphoric acid)-acetonitrile(90:10), and the column temperature was 40℃. CONCLUSION The chromatographic conditions optimized by central design-response surface method can be used for the determination of related substances in Matrine and Sodium Chloride Injection. The method has high accuracy and good repeatability.