Objective To isolate, culture and identify the pathogenic bacterium from 6 cases of bacterial pneumonia within 1 month in tree shrew. Methods We Dissected the dead tree shrew ,cut open the lung tissue with sterile blade to insert focus of infection in the lung with inoculating loop to get samples for inoculating on nutrient agar and another two samples for bacterial smear with Gram staining and acid-fast staining. The bacterium obtained was isolated and cultivated for bacterial growth observation, then the pathogenic bacterium of tree shrew and its antibiotic susceptibilities was initially identified by Gram staining, acid-fast staining, oxidase test, biochemistrical encoding Identification system and 9-kind antibiotic susceptibility test. Results A amount of negative bacteria were observed from samples with Gram staining. Acid-fast staining appears it was nontuberculous mycobacterium about size 0.2μm?～6μm. Only 1 strain strong bacterium was observed in every 6 case on nutrient agar plate, it was verified as Gram-negative bacterium and nontuberculous mycobacterium, its size and staining results were the same as samples. It was identified as enteropathogenic E.coli. Antibiotic susceptibility test shows it is highly susceptibility to cefoperazone, furantoin, ampicillin, amikacin, ofloxacin, norfloxacin, sulfonamide methoxybenzyldine and low susceptibility to gentamicin and penicilin. Conclusion We conclude that Bacterial pneumonia is the cause of these 6 tree shrew death cases, the enteropathogenic E.coli.was initially identified as the reason. Drugs selected by antibiotic susceptibility could instruct clinical treatment like these cases in tree shrews.