OBJECTIVE To study the lower respiratory tract infection caused by Stenotrophomonas maltophilia and the resistance situation. METHODS The clinical data of 79 cases of lower respiratory tract infection caused by(S.maltophilia) were analyzed and the susceptibility test was made using ATBPSE5 kits. RESULTS All patients had clinical symptoms,and the rate of empirical using of broad-spectrum antibiotics reached to 100%.In all these patients,74.68% were older than 60,and 51.90% received invasive operation such as trachea intubation or incision,and the immmunosystem function of 62.03% was compromised.All these were high risk factors resulting in the lower respiratory S.maltophilia infection.All cases showed resistance to most broad-spectrum antibiotics except ticarcillin/clavulanic acid and sulfamethoxazole/trimethoprim(Cotrimoxazole).The latter two antibiotics still showed high sensitivity to the pathogen. CONCLUSIONS It is necessary to avoid the risk factors causing nosocomial(S.maltophilia) infection.Ticarcillin/clavulanic acid and Cotrimoxazole are the first choice for clinical treatment.Using fluoroquinolone and ceftazidime simultaneously can improve the curing rate.