OBJECTIVE To evaluate the rationality of clinical application of polymyxin B in the inpatients of a third grade class A hospital，so as to provide evidence for the optimization of clinical scheme of the drug. METHODS A retrospective method was conducted on the electronic medical records of inpatients treated with Polymyxin B sulfate for injection from January 2020 to March 2022 to collect the basic information of patients， inpatient departments and time， infection diagnosis， results of pathogenic bacteria test， laboratory test indicators， usage and dosage， and combined medication，etc. Based on the drug instructions， according to relevant guidelines and consensus， the rationality， efficacy and safety of polymyxin B in inpatient were evaluated. RESULTS & CONCLUSIONS A total of 101 inpatients were included， respiratory system infection was the main cause （62.4%）. All patients had received the etiological examination， and the pathogen with the highest detection rate was carbapenem‑resistant Acinetobacter baumannii （40.6%）. One hundred patients were treated by intravenous drip， and 4 patients were treated by combination of aerosol inhalation or intrathecal injection； 99 patients were given the dose of 500 thousand units by continuous intravenous infusion， q12 h. Totally 51.5% of patients were treated for 7-14 days； and 77 patients were treated with other anti-Gram-negative drugs. There were unreasonable phenomena including too short time of medication （29.7%）， no combination of medication （23.8%）， and no indication of medication （17.8%）. The clinical effective rate of 101 patients treated with polymyxin B was 49.5%， and 16 patients （15.8%） had acute kidney injury during the treatment. Clinical pharmacists should actively participate in the clinical treatment of polymyxin B， formulate individualized treatment plans according to the guidelines/consensus and in combination with the patient’s condition and infection status to improve the rationality of clinical medication.