Abstract: A total of 102 single-spore isolates were collected from cucumber or tomato infected by Botrytis cinerea without exposure to SYP-Z048 in protected fields in different regions of Hebei Province.The sensitivity of the isolates was determined by mycelial growth rate inhibition tests.The EC50 value distributed as a unimodal curve,which ranging from 0.046 0 μg/mL to 0.199 1 μg/mL,with a mean value of (0.118 2±0.036 3) μg/mL.The data could be used as baseline sensitivity of B.cinerea to SYP-Z048.Seven SYP-Z048-resistant mutants were obtained through ultraviolet radiation.The colonies diameter,mycelial weight,sporulation and pathogenicity ability of resistant mutants were significantly lower than that of parental isolates.The resistance rate of resistant mutants receded after nine incubations.