Abstract: It is crucial and helpful for plant disease management to detect resistance level of fungicide.Baseline sensitivity of Phytophthora nicotianae to fungicide dimethomorph was established based on in vitro assay and the dimethomorph resistance level of black shank pathogens collected from different tobacco planting zones in Dali were measured.The results showed that baseline sensitivity of P.nicotianae to dimethomorph was 1.4656 μg/mL.The range of EC₅₀ values of all sixty-eight field isolates to dimethomorph was 0.5857 to 2.5254 μg/mL, in which average value was 1.1118 μg/mL.This result suggest that P.nicotianae isolates collected from Dali were high sensitive to dimethomorph and the resistance risk of black shank pathogens was low.Dimethomorph can be deployed to prevent tobacco black shank effectively, but it should be a reasonable rotation with different fungicides.