To separate ACE inhibitors from edible plants, spices, and herbs, 285 extracts of 95 sources were screened for ACE inhibitory activity. The extract of Sinapis alba L. had the most potent ACE inhibitory activity. Mustard seeds were crushed homogeneously and extracted with hexane and water successively. Lyophilized water extract was fractionated with $H_2O$:butanol(1:1). The ACE inhibitor was purified from butanol fraction by methanol precipi-tation, gel filtration, HPLC, and FPLC with Superdex peptide HQ 10/30 column. The active fraction has been purified to homogeneity, which was proven by gel filtration using FPLC system. The yield was 0.02%. The com-pound has a molecular weight of about 640. The compound competitively inhibited ACE activity and the $IC_{50}$ value was 79$mu extrm{g}$/ml. The purified compound showed uterus contraction activity in isolated rat uterus.