Abstract: Microcellulose TLC dual wavelength TLC scanning method for determination of vitamin U (3-amino-3-carboxypropyl) dimethyl sulfonium chloride in tablets was employed with n-butanol-acetone 25-28% ammonia water-water ( 40:40:8:25)as developing solvent system and ninhydrin as color reagent. The R_f values of vitamin U and its decomposition product were 0.37 and 0.63 respectively.After separation cf vitamin U from its decomposition product, the dual wavelengthTLC scanning with external standard (measuring wavelength is 560nm, reference wavelength is 750 nm) was used. The recovery is 98.7% (n = 7 ).