Abstract: Matrine, oxymatrine, sophocarpine, oxysophocarpine and sophoridine in Sophora flavescens Ait. and its preparations can be separated on silica gel G thin layer. The alkaloid was visualized by spraying with a detecting reagent, collected in a collector, elu-ted with an eluting solvent to form an ion pair with bromothymol blue in pH 7.6 buffer solution, extracted into chloroform and then determined colorimetrically at 420 nm The total alkaloid content can be determined colorimetrically without thin layer separation.For matrine, sophocarpine and sophoridine, benzene-acetone-ethyl acetate-cone, am-monia water (2:3:4:0.2)was used as a developing solvent, modified Dragendorff rea-gent as a detecting reagent, and 95% ethanol(containing ammonia water)as an eluting sol-vent. While for oxymatrine and oxysophocarpine, chloroform-methanol-cone, ammonia water (5:0.6:0.3) was used as a developing solvent, 0.5% morin in ethanol as a detect-ing reagent (only 85-90% recovery of oxymatrine from the thin layer when Dragen-dorff reagent or iodine vapor was used as the detecting reagent), 95% ethanol as an elu-ting solvent, a layer of 5 mm thick of alumunium oxide was first introduced into the collector for retaining morin from being elutedThe results of analysis were accurate and reproducible.