Abstract: Objective To evaluate the distributions and drug resistance of the pathogenic bacteria causing lower respiratory tract infection in patients with malignant tumor. Methods A retrospective study was conducted of the distributions and drug resistance of the pathogenic bacteria in the lower respiratory tract specimens of 244 patients with malignant tumor and concurrent lower respiratory tract infection. Results The most common pathogens causing lower respiratory tract infection are Gram-negative bacilli,24.01% of which are K.pneumoniae,20.96% P.aeruginosa,and 20.52% E.coli. Conclusion The bacterial constitution in the lower respiratory tracts of patients with tumor in our tumor ward is different from that in other hospitals. The drug-resistance rate of the third generation cephalosporin and amino glycoside antibiotics in our hospital is lower than that in other hospitals. Therefore,they should be used as experiential first-line drugs.