Previously, the methanolic extract of Paeonia lactiflora seeds was shown to have strong ingibitory activity against soybean liposygenase (SLO). Four phenolic compounds were isolated from the seeds by solvent fractionation Sephadex LJ-20 column chromatography and preparative HPLC, and three of them showed strong SLO inhibitio and were characterized as trans-resveratrol, $varepsilon$-viniferin and luteolin by UV, IR, 1H-NMR, 13C-NMR and MS spectrometry. trans-Resveratrol (IC50=1.02$mu$M), $varepsilon$-viniferin (IC50=0.81$mu$M) and luteolin (IC50=10.01$mu$M), first found in the above seeds, exhibited a potent SLO inhibitory activity although their activity was lower than that of a well-known lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA) (IC50=0.57$mu$M). These results suggest that Paenia lactiflora seeds, now an unused plant seed, may be developed into useful sources of anti-inflammatory drugs.