In order to established a method for simultaneous determination of isoquercitrin, astragaline, quercetin and kaempferol in Lysimachia clethroides, the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6) methanol was used as the ultrasound-assisted extraction solvent combing with RP-HPLC. A Purospher star RP-C1 column was used with the mobile phase of aceto- nitrile, methanol and 0. 4% phosphate acid by gradient elution at the detection wavelength of 360 nm. The flow rate was 0.7 mL x min(-1), and the column temperature was the room temperature. Under the optimized conditions, the linear ranges were 2.54 x 10(-2)-2. 54, 2.50 x 10(-2)- 2.50, 1.54 x 10(-3)-0.154, 1.49 x 10(-3)-0.149 microg for isoquercitrin, astragaline, quercetin and kaempferol, respectively. The average recoveries of the four constituents were 101.1%, 98.90%, 101.0%, 101.6%, respectively. The method was green, simple, rapid and accurate, and provided a valid method for analysis of isoquercitrin, astragaline, quercetin and kaempferol in L. clethroides.