Abstract: This paper studied on antimicrobial effect of medical plant. In other words, the antimicrobial circle, MIC and MBC were tested. The extracted constituents showed stability against high temperature. The results showed: the Berberis heteropoda pigment could effectively inhibit the growth of theE scherichiac oli, the calyx pigment ofP hysalis alkekengi coulde ffectively inhibit the growth of the Bacterium proteus, the concentrated liquid of Rhodiola sachalinensis could effectively inhibit the growth of the Bacillus subitilis, the concentrated liquid of Foeniculum vulgare Mill has no antimicrobial effect on the four bacteria.The MIC and MBC of the Berberis heteropoda pigment affecting 4 species of bacteria respectively were: and Bacillus subitilis: MIC 2. 5%, MBC 5.0%, Escherichia coli: MIC 5.0%, MBC 5.0%, Staphylococcus aurous: MIC 2.5%, MBC 5.0%, Bacterium proteus: MIC 1.25%, MBC 1.25%. The MIC and MBC of the calyx pigment of Physalis alkekengi respectively were: Bacillus subitilis: MIC 4.18%, MBC 4.18%, Escherichia coli: MIC 8.35%, MBC 8.35%, Staphylococcus aurous: MIC 4.18%, MBC 4.18%, and Bacterium proteus: MIC 4.18%, MBC 8.35%. The MIC and MBC of the concentrated liquid of Rhodiola sachalinensis respectively were: Bacillus subitilis: MIC 2.09%, MBC 4.18%, Escherichia coli: MIC 2.09%, MBC 2.09%, Staphylococcus aurous: MIC 8.35%, MBC 8.35%, and Bacterium proteus: MIC 4.18%, MBC 8.35%. The antimicrobial activity of the three extracts under high temperature was stable. However, the antimicrobe mechanism needed further study.

Key words: natural pigment, concentrated liquid, antimicrobial effect