Abstract: The mutants in different resistance level of Rhizoctonia cerealis to tebuconazole were selected on PDA medium amended with the fungicide and irradiated by UV respectively. Then changes of the sensitivity to osmolarity and relative leakage at different concentrations of tebuconazole in different times were compared between resistant strains and sensitive strain respectively. In the same concentrations of dextrose, the sensitive strain was inhibited more than all resistant strains. All the resistant strains had no obvious difference on the PDA containing 1% and 4% dextrose, but have some difference on the 4% dextrose medium in mycelium growth. However, the sensitive strain was more sensitive to 1% and 8% dextrose compared with 4% dextrose medium. The results of relative leakage showed that, the resistant strains could leak more electrolyte than the sensitive strain in 1 h after treatment with different concentrations of tebuconazole. However, the relative leakage of sensitive strain was higher than that of resistant strains finally. In addition, the relative leakage of resistant strains treated with high concentrations of tebuconazole was higher than treated with low concentrations.