This invention provides a novel mycovirus for inhibiting pathogen of rice blast disease and a novel method for preventing the said plant disease.The novel mycovirus is intrinsic in certain pathogens of rice blast disease, which has 2.8~3.6kb of four double-stranded RNAs and can inhibit the plant pathogenic fungi. The mycovirus can inhibit the plant pathogenic fungi, therefore, it is suitable for attenuating the plant pathogenic fungi and preventing plant diseases. In addition, the mycovirus differs from those known mycovirus. Advantageously, the novel mycovirus can exist in the outside of the cell, the said mycovirus therefore can directly infect the host cells without depending mycelia fusion.
