[Objective] To isolate and identify the antimicrobial active component extracted from fermentation broth of antagonistic actinomycetes strain G-19 against peach crown gall (Agrobacterium tumefaciens). [Methods] Sephadex LH-20 chromatography, HPLC and middle-pressure chromatography were used for isolation and purification. LC-MS, NMR were applied to identify structure of the active component. [Results] Compound G-19-I was isolated and structurally identified as 1,2-benzenedicarboxylic acid, 1,2-dibutyl ester (DBP); compound G-19-II was isolated and structurally identified as 2-(4-hydroxyphenyl)-3,4-dihydro- 2H-chromene-3,4,5,7-tetrol, commonly known as leucopelargonidin. [Conclusion] The material basis of the antibacterial constituents in antagonistic actinomycetes strain G-19 was further clarified.