Abstract: In order to screen the effective inhibitors of phenoloxidase from Spodotera exigua,three compounds were isolated from the ethanol extracts of Trollius ledebouri with traditional isolation and preparative HPLC methods. The structures were determined to be methyl 3,4-dihydroxybenzoate (compoundⅠ),2″-O-(2methylbutyryl)vitexin (compound Ⅱ) and Ursolic acid (compound III) based on spectral methods,respectively. In addition,the effects of the compounds on phenoloxidase (PO) activity of Spodotera exigua were also investigated. The results indicated that the three compounds showed different inhibitory effects on the PO and the inhibitor concentrations leading to 50% (IC50) activity lost were estimated to be 2.04 mmol/L for compound Ⅰ,0.83 mmol/L for compound Ⅱ and 0.32 mmol/L for compound Ⅲ,respectively.