Objective To investigate the characteristics,clinical indicators and risk factors of levofloxacin-induced arrhythmias in large hospitalized populations.Methods Using the"Adverse Event Active Monitoring and Intelligent Assessment Alert System-Ⅱ"(ADE-ASAS-Ⅱ),the electronic medical record of inpatients using levofloxacin in 2019 was monitored to obtain relevant data for patients with arrhythmias.Patients without arrhythmia were selected by propensity score matching,and the risk factors of levofloxacin-induced arrhythmias were analyzed by univariate and multivariate conditional logistic regression.Results The incidence of levofloxacin-induced arrhythmias was 1.64％in 12 879 people who used levofloxacin.The incidence in people over 65 years was 3.22％.The main manifestations of levofloxacin-induced arrhythmias were extrasystole(0.84％),tachycardia(0.63％),QT interval prolongation(0.44％),and no severe arrhythmias such as torsades de pointes and ventricular fibrillation.Multivariate Logistic regression analysis showed that the course of administration(OR=1.030,95％CI 1.009 to 1.050,P=0.004)and intravenous administration(OR=2.392,95％CI 1.478 to 3.870,P＜0.001)independent risk factors for levofloxacin-induced arrhythmias.Conclusion Arrhythmias caused by levofloxacin are common and have various types,among which the occurrence of QT interval prolongation is occasional.We should pay more attention to elderly patients who receive intravenous levofloxacin and try to avoid long courses of medication.