Abstract: This paper reports a quantitative determination of the contents of flavonoids in Rhododendron leaves by HPTLC scanning method. The methanol extract of each sample was spotted on a HPTLC silica gel plate (E.Merck F₂₅₄)alongside with standard substances. Using the upper layer of petroleum ether(60～90℃)-ether-formic acid (62: 31:7) as developing solvent Ⅰ, farrerol, kaempferol and quercetin were well separated. The spots were determined by a single wavelength (366 nm) TLC-scanner, Camag model 76510. The same plate was then further developed by developing solvent Ⅱ.7 ml of the lower layer of chloroform-methanol-water (7: 3:1) plus 0.5 ml of formic acid to separate polystachoside, quercitrin and hyperoside. The densitometric determination of each spot was also carried out with the same scanner.The contents of 6 flavonoids in the leaves of 166 Rhododendron species were thus determined.