Abstract: OBJECTIVE To study the impurity profile of omeprazole sodium for injection by qualitative and quantitative analysis on the related substances of it. METHODS Chromatographic separations were performed on an ACES-AQ column(4.6 mm×250 mm, 5 μm). The gradient elution employed solutions A and B as mobile phase components. The solvent A was phosphate buffer (pH 7.0)-acetonitrile(75:25), while solvent B was acetonitrile. The mobile phase was pumped at 1.0 mL·min^-1. The detection wavelength was 280 nm. Twelve known impurities and other four unknown impurities in omeprazole sodium for injection were quantitatively determined by principal component self-control method with correction factor. The structures of four unknown impurities were inferred by high-performance liquid chromatography-triple quadrupole mass spectrometry. RESULTS Omeprazole and its related substances had good separation. The correction factors of nine impurities ranged from 0.48 to 1.14. Three to eight impurities were detected in omeprazole sodium for injection produced from different enterprises. CONCLUSION The developed method with good specificity can be used for the separation and determination of related substances in omeprazole sodium for injection and can help for the impurity control of omeprazole sodium for injection.