Corn stalk rot occurs in corn in Jilin province. The earlier the infecting stage is and the moreserious the degree of disease is, the more yield loss occurs. The yield loss may be estimated by therate of infected plant at various growing stages and the degree of disease in field. In Jilin province, three fungi isolates, pythium aphanidermatum, Fusarium graminearum and F. moniliforme are themost frequently distributed and have the highest virulenty, being considered as the dominant pathogens of corn stalk rot.