OBJECTIVE：To establish a method for the determination of the content and molar ratio of Ornithine aspartate for injection. METHODS：HPLC was performed on the column of Thermo HYPERSIL Aps-2 amino column with mobile phase of acetonitrile- 0.05mol/L Potassium dihydrogen phosphate solution，the flow rate was 0.9 ml/min，the column temperature was 30 ℃，the detection wavelength was 200 nm，and the injection volume of 20 μ l. 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，stability 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 determined by potentiometric titration with national standards. CONCLUSIONS：The method is simple，accurate，specific and sensitive， and suitable for the determination of the content and molar ratio of Ornithine aspartate for injection.