Objective:To investigate the efficacy and nephrotoxicity of high-dosepolymyxin B (PMB) in treatment of patients with multidrug-resistant Gram-negative bacteria (MDR-GNB) infections.Methods:Clinical data of 90 patients with MDR-GNB infections who admitted to the Affiliated Huaian First People′s Hospital from January 2018 to December 2020 were retrospectively analyzed. Thirty one patients receivedhigh-dose PMB(≥25 000 U·kg?1·d?1) for treatment (high-dose group) and 59 patients received standard-dose PMB(<25 000 U·kg?1·d?1) for treatment (control group). The curative effect and renal function of the two groups were compared. The factors related toacute kidney injury (AKI) were analyzed with logistic regression.Results:The daily PMB dose and treatment course in high-dose group were (29 800±4 500) U/kg and (9.16±4.15) d, while those of the control group were (17 300±3 500)U/kg and (7.32±3.87) d ( P<0.01). The effective rate of the high-dose group was higher than that of control group (83.9% vs. 61.0%, χ2=4.95, P<0.05).The creatinine levels in high-dose group were increased significantly from 69.40(47.00, 94.70)μmol/L before treatment to 116.20(59.20, 213.20)μmol/L after treatment ( Z=-2.99, P<0.01); while there were no significant changesin control group before and after treatment [55.00(37.00, 92.47)μmol/L vs. 50.10(34.00, 156.00)μmol/L, Z=-1.78, P=0.78]. The 30-day mortality rate in the high-dose group was 32.3% (10/31), that in the standard-dose group was 49.2% (29/59)(χ2=2.36, P=0.12). The AKI incidence rate in high-dose group was higher than that in standard-dose group [ 67.7% (21/31) vs. 45.8% (27/59), χ2=3.94, P=0.04]. There were 4 and 10 deaths due to AKI in the high-dose and standard-dose groups, respectively (χ2=0.25, P=0.61). Logistic regression analysis showed that daily high-dose PMB was independently associated with AKI( OR=2.662, 95% CI:1.082-6.549, P=0.03). Conclusion:Thehigh-dose PMB is effective in treatment of patients with multidrug-resistant Gram-negative bacteriainfections, but the incidence of AKI is also significantly increased. Therefore, when using daily high-dose PMB, the pros and cons must be weighed to avoid increasing the risk of AKI.