Abstract: The physical-chemical characteristics and chemical type of the bioactive substance obtained from the fermentation broth of actinomyces strain A01 were studied. The bioactive substance showed high inhibitory activity to many plant pathogenic fungi such as Botrytis cinerea and Fusarium spp.. The ion characteristics and chemical type identification of the antibiotics were analysized by paper chromatography, paper electrophoresis and UV absorption spectrum. The results showed that the bioactive substance in neutral and alkaline environment was relatively stable. Its relative activity remained at 81.19% when treated 30 min under 100 ℃. It was not sensitive to protease, but more sensitive to UV. UV spectrum showed that the active compound presented three typical absorbance peaks at 291 nm, 305 nm and 319 nm, which is the typical characteristic of conjugated polyene chemicals. Combining the results of paper chromatography and paper electrophoresis, we may infer that the active substance produced by strain A01 could be a tetar-alkene neutral antibiotic. This study provides valuable information for the purification of the active substance and its further agricultural application.