Abstract: A simple, sensitive and accurate method for separation and determination of the alkaloids, 1-formyl-β-carboline (Ⅰ),. 4, 5-dimethoxycanthin-6-one (Ⅱ), 1-vinyl-4, 8-dimethoxy-β-earboline (Ⅲ) and 1-formyl-4-methoxy-β-carboline (Ⅳ), in Ku-Mu Picrasma quassioides (D. Don) Benn. is described.Sample solution was applied at a point 1 cm from the bottom edge of the HPTLC silica gel plate (10 × 10cm). Chloroform (water saturated)—methanol (40:0.5) was used as the developing solvent. The plate was saturated for 30 min and then developed twice for 9 cm using ascending technique. The plate was fumigated with formic acid for 1 h at room temperature to intensify the spot color. The spots were scanned with a Sehimadzu CS-910 TLC scanner. The content of four alkaloids in Ku-Mu was calculated by comparison with standards spotted on the same plate.The standard curve was linear in the range oft the 0.05～0.30 μg for the four alkaloids. The method has been applied to the analysis of different samples. This method can be used for the quality control of Ku-Mu preparations for clinical use.