OBJECTIVE:To establish a method for the determination of the content and molar ratio of Ornithine aspartate for in-jection. METHODS:HPLC was performed on the column of Thermo HYPERSIL Aps-2 amino column with mobile phase of aceto-nitrile-0.05mol/L Potassium dihydrogen phosphate solution,the flow rate was 0.9 ml/min,the column temperature was 30℃,the de-tection wavelength was 200 nm,and the injection volume of 20 μl. The results determined by HPLC and potentiometric titration were compared. RESULTS:The linear range of ornithine aspartate was 0.02-10.01 mg/ml(r=0.999 9);RSDs of precision,stabili-ty and reproducibility tests were lower than 2%;recovery was 99.15%-100.15%(RSD=0.35%,n=9). The content of 3 batches of Ornithine aspartate for injection was 100.04%-100.64% and molar ratio was 0.982-0.989. The content is similar to the results de-termined by potentiometric titration with national standards. CONCLUSIONS:The method is simple,accurate,specific and sensi-tive,and suitable for the determination of the content and molar ratio of Ornithine aspartate for injection.