A method was developed in this study to fast and accurately determine pathogenicity of Fusariumoxysporum causing root rot of soybean at seedling stage. The method was used to study interactions between 6 stainsof F. oxysporum and 11 soybean cultivars. Results showed that there were significant differences among the cultivarsin resistance to the disease. Mean disease indices were 15.24, 44.90, 19.31, or 71.43 in the interactions between Su-inong 28 and strain K31, Suinong 28 and strain YA25, Dongnong 54 and strain M63, and Dongnong 54 and strain H1, respectively. The results indicated that this method could be applicable to large-scale, fast and accurate deter-mination of pathogenicity of F. oxysporum and screening of host resistance in interactions between the pathogen andsoybean cultivars or lines.