The methanol extract of Thalictrum uchiyamai Nakai was fractionatedi nto four parts; (1) ether soluble nonphenolic fraction (2) phenolic tertiary bases fraction, (3) chloroform soluble tertiary bases fraction and (4) aqueous quaternary bases fraction. The fractions of this plant showed a total of twenty-four spots on the silica gel TLC. Ether soluble nonphenolic fraction and ether soluble phenolic fraction showed nine alkaloid spots respectively, chloroform soluble fraction showed three alkaloid spots and quaternary bases fraction showed three alkaloid spots. The antimicrobial activity of the four extracts was shown as follows; nonphenolic tertiary bases inhibited the growth of Micrococcus dutica at the concentration of $50mu$g/ml, in phenolic tertiary bases $500mu$g/ml concentration was inhibitory to Micrococcus dutica and to Staphyloccus aureus. In aqueous quaternary bases, $500mu$g/ml concentration was inhibitory to Klebsiella pneumonae. Chloroform soluble tertiary fraction showed slight activity. All of bases showed reproducible activity against tested microorganisms.