OBJECTIVE To observe activity of isoniazid gel against mycobacterium tuberculosis in vitro and its safety in bronchia interventional therapy.METHODS The MIC and MBC of isoniazid and isoniazid gel were measured by hand and instrument method, the safety of isoniazid gel was assessed by bronchia interventional therapy using rabbits as experiment animals. RESULTS The MIC of isoniazid gel to M. tuberculosis H 37 RV and M. bovis was 1 mg·L -1 , to M.phlei was 8 mg·L -1 , the MBC of isoniazid gel to M. tuberculosis H 37 RV and M. bovis was 4 mg·L -1 ,to M. phlei was 16 mg·L -1 , the MIC and MBC of isoniazid gel and isoniazid had no significant difference; the animal safety experiment was negative.CONCLUSIONS These results suggest that isoniazid gel and isoniazid have the same efficacy against mycobacterium tuberculosis, carbomer doesn't affect the activity of isoniazid against mycobacterium tuberculosis; isoniazid gel which contains carbomer is safe in bronchia interventional therapy.