Abstract: Application of thin-layer chromatographic method for separation and subsequent visible densitometric determination of protopine (Ⅰ), d-isocorynoline (Ⅱ), d-corynoline (Ⅲ), tetrahydrocoptisine (Ⅳ), acetylcorynoline (Ⅴ) and tetrahydrocorysamine (Ⅵ) in Conydalis bungeana is described. The procedure is as follows:Sample preparation: 0.5 g of pulverized sample of crude drug is macerated overnight with 10 ml of chloroform saturated with 25% NH4OH in a glass stoppered flask. The extract is filtered and exactly 5 ml of the filtrate are evaporated to dryness. The residue is dissolved in 1 ml of chloroform.Detection and identification of alkaloids in extract: Thin layer chromatography: Basic silica gel G plates (15×15 cm); Developing solvent: hexane-chloroformmethanol A. 8:2:0.25;B. 4:5:1. Detection of spots by spraying with modified Dragendorff's reagent. Rf values of Ⅱ, Ⅲ, Ⅳ, Ⅴ and Ⅵ are 0.13, 0.28, 0.46, 0.56 and 0.79, respectively with A. Rf vatue of I is 0.58 with B.Estimation of alkaloid contents: After spraying, the plate is covered immediately with a glass plate of the same size and left to stand for 2 hours to allow the spots to reach stability. The spots are scanned with a Shimadzu Dual-Wavelength TLC Scanner CS-910. The results are calculated by comparison with standards spotted on the same plate.