Abstract:[Objective] Toxin produced by phytopathogenic fungi is one of the important microbial herbicides. We found a new compound with herbicidal activity. [Methods] Five different ultraviolet absorption components were isolated from the filtrate of Botrytis cinerea isolate 7–3 culture. [Results] Of the five components, one showed strong inhibitory to Digitaria sanguinalis. The pure fraction with high herbicidal activity was obtained by HPLC purification. Its structure was identified as 10–syn–dihydrobotrydial by Ultraviolet and Visible Spectroscopy, Infrared Spectrum, Nuclear Magnetic Resonance Spectroscopy analysis. [Conclusion] The findings are important for future preparation and application of the herbicide.