Abstract: In order to evaluate the sensitivity and the resistant mechanism of Botrytis cinerea Pers. (the causal agent of gray mold disease) from strawberry to boscalid, the sensitivity of 195 isolates in 6 districts in Shanghai were tested with petri plate. And the succinate dehydrogenase subunits genes of 20 isolates with different sensitivity were sequenced. The results showed that the lowest EC₅₀ value of mycelial growth inhibition was 0.15 μg/mL, and the highest value was over 110 μg/mL. The lowest EC₅₀ value of conidial germination was 0.19 μg/mL, while the highest value was over 50 μg/mL. In Shanghai, the resistance frequency was 29.74% (resistance factor >10), and the frequency of high resistance was 20.51% (resistance factor >100). Resistance mechanism analysis indicated that the resistance to boscalid could be attributed to point mutations at codon 272 or 225, which would lead to the substitution of histidine to arginine (H272R), or proline to phenylalanine (P225F) in SdhB subunit of succinate dehydrogenase. And the H272R substitution was more common. This study showed the high resistance level and frequency to boscalid of B. cinerea from strawberry in Shanghai, and revealed that the H272R substitution in SdhB could be the main cause of the resistance.