OBJECTIVE： To probe the role of clinical pharmacists in drug use of patients with severe pneumonia. METHODS： Clinical pharmacists participated in the treatment for a patient with ESBLs producing Klebsiella pneumoniae severe pneumonia. The patient was given cefoperazone tazobactam combined with moxifloxacin and ganciclovir initially. Clinical pharmacists suggested stopping cefoperazone tazobactam and moxifloxacin and additionally using meropenem according to the elevation of hemogram infection indexes； suggested stopping ganciclovir and continuously using meropenem according to the results of sputum culture； suggested providing cefoperazone sulbactam de-escalation sequential therapy for ESBLs producing Klebsiella pneumoniae and stopping cefoperazone sulbactam and azithromycin according to clinical symptoms of the patient. RESULTS： The physicians adopted the suggestions of clinical pharmacists. After treatment， body temperature and lab indexes of the patient recovered to normal； the result of sputum culture turned to negative. Chest CT showed that the infection focus was obviously absorbed compared to before. After discharged from hospital and followed up， the patient was found to have a good prognosis. CONCLUSIONS： Through actively participating in drug therapy， based on lab indexes and results of sputum culture， clinical pharmacists provide pharmaceutical care and adjust medication plan to improve treatment rate of patients with severe pneumonia and the safety and effectiveness of drug treatment， be of great significance to promote the rational use of antibiotics.