To identify the sensitivity of the main soil-borne pathogens of tobacco such as Phytophthora nicotianae and their candidate biocontrol strains such as Trichoderma harzianum to dimenthomorph,mycelium growth rate method,spore inhibition method,dilution-plate method were used to determine the inhibitory effect of dimethomorph on mycelium growth of P.nicotianae,Pythium aphanidermatum,Rhizoctonia solani,Fusarium solani,T.harzianum,sporangia production of P.nicotianae and conidia differentiation of T.harzianum,and on Bacillus subtilis,Streptomyces aureoverticillatus.The results showed that dimethomorph had a significant inhibitory effect on mycelium and sporangia of P.nicotianae,and the EC50 value of its mycelium growth was 0.467 6 μg/mL;and it had no strong effect on P.aphanidermatum,R.solani,F.solani,T.harzianum,B.subtilis,S.aureoverticillatus.Therefore,dimethomorph can be mixed with the candidate biocontrol strains to control tobacco black shank.