Objective: To establish a high performance liquid chromatog. method for the determination of related substances in compound amino acid 15) dipeptide 2) injection.Methods: Inert Sustain AQ-C18 (4.6×250mm, 5μm) chromatog. column was used, 0.05mol/L sodium dihydrogen phosphate solution (pH=2.1) was used as the mobile phase, the flow rate was 1.0mL/min and the detection wavelength was 205 nm, the column temperature was 18°C and the injection volume was 50 μL.Results: Under the selected chromatog. conditions, (S) -3- (3, 6-dioxo-2-piperazine) propionic acid, cyclo- (glycylglutamine) peaks and pyroglutamic acid peaks were consistent with The resp. adjacent peaks can be separated; the injected amounts of (S) -3- (3, 6-dioxo-2-piperazine) propionic acid, cyclo- (glycylglutamine) and pyroglutamic acid are The peak area showed a good linear relationship (r>0.999); the RSDs of the three impurities in the precision test were all less than 1.0%; (S) -3- (3, 6-dioxo-2-piperazine) propionic acid, cyclic The quantification limits of - (glycylglutamine) and pyroglutamic acid were 0.85ng, 0.29ng and 0.28ng, resp. and the detection limits were 0.25ng, 0.095ng and 0.05ng, resp.; the recoveries were all in the range of 98% to 102%.The samples were collected by elution through the column and verified by the elution curve, it was determined that the impurities could be completely and effectively eluted.Conclusion: The method has strong specificity accurate results and high sensitivity, which can be used for the determination of related substances in compound amino acid 15) dipeptide 2) injection and is suitable for product quality control.