Abstract: Vitamin U is a commonly used combined drug for treatment of ulcer of digestive nature. Its chemical name is [(3-Amino-3-carboxypropyl)dimethyl sulfomium chloride].In this paper we have used the paper chromatography with N-butanol-95% ethanol-formic acid-water (77:15:20:20) as developing agent. We have separated and identified anti-moisture granule of vitamin U,and determined Rf value of each component.After separation of vitamin U from its decomposition products, serine, glycine etc., we availed ourselves of the dual-wavelength TLC scanner connected with the processor, and used external comparison method and relative percentage quantitative method to determine the content.This method has proved to be accurate, sensitive and simple in operation.