Abstract: Objective To investigate the clinical characteristics, pathogen constitution and their tolerance to antibiotics in idiopathic inflammatory myopathies (ⅡM) patients complicated with pneumonia and the associated risk factors. Methods The clinical data and pathogen test results of 93 ⅡM patients with pneumonia and 52 ⅡM patients without pneumonia (control group) were retrieved and compared. Results Age of onset and interstitial lung disease were identified as risk factors associated with ⅡM complicated with pneumonia. Gram negative bacteria were the most common pathogen. Klebsiella pneumoniae was the most common bacteria and Candida albicans was the most common fungus causing infections in the ⅡM patients, which were relatively sensitive to the third- and fourth-generation of antibiotics such as cephalosporin, fluoroquinolones and aminoglycoside. Conclusion Older patients with interstitial lung disease are prone to having pneumonia, especially those caused by gram negative bacteria and other atypical pathogens. Timely and reasonable anti-infection treatment is essential.