Abstract: The mutants in different resistence level of Sclerotinia sclerotiorum to dimethachlon were selected on PDA medium amended with the fungicide from 0.5 μg·ml -1 to 50.0 μg·ml -1 . The growth of mutants MN61(MR)and MN91(HR) was inhibited on the PDA containing 1% and 8% dextrose, and MN113(LR) was only sensitive to 1% dextrose compared with their parents incubated on the 2% dextrose medium. Dimethachlon caused more electrolyte leakage of the mutant cells than that of its parent isolate. The activity of PAL( L-phenylalanine ammonia lyase) of mutant MN61 was higher than that of sensitive isolate PN061 when they were incubated in the solution of nutrient deficieny or treated with 5 μg·ml -1 or 20 μg·ml -1 dimethachlon.