With the development of nanoscience and nanotechnology, increasing research focuses on synthesis, characterization and application of silver nanoparticles. Reported here is the synthesis of silver nanoparticles using Osmanthus fragrans leaf extract, as well as several optimized synthesis parameters, including quantity of fern leaves, concentration of AgNO3, pH, and regulation of reaction temperature. Antifungal activity of silver nanoparticles on Bipolaria maydis (AH-B06) was measured through colony formation and inhibition zone methods. The optimal biosynthesis system contained 5 g of fern leaf and 1 mM AgNO3 at pH 9.0 and 60°C. Under said conditions, the resulting synthesized nanoparticles were nearly spherical, with an average size of 20 nm. In tests, silver nanoparticles synthesized at different concentrations of AgNO3 inhibited colony formation to varying degrees, resulting in different inhibition zones. No colony formed on PDA plates at AgNO3 concentrations at or over 2 mM, while quantity of herbal component was unchanged. Regarding inhibition zones, diameters increased gradually at AgNO3 concentrations from 1-8 mM, while antifungal effect reached maximum at 5 g of herbal component. Results of this study offer a new approach and novel material for comprehensive control pathogenic fungi on plants. As well, the presented method and material have potential application for screening novel fungistats with high efficiency and low toxicity, thus offering a green chemistry answer to a worldwide need.