This study is designed to investigate the effects of chinfloxacin hydrochloride (CFX) on the kinetics of HERG K⁺ channel.  Whole cell patch clamp technique was used to record HERG K⁺ currents from HEK293 cells transiently transfected with cgi-HERG-GFP plasmids and channel kinetics were assessed in the absence and presence of CFX and moxifloxacin hydrochloride (MOX).  Results demonstrated that the open state of HERG K⁺ channel was inhibited by CFX in a concentration- and time-dependent manner, with an IC₅₀ of 162.1 ± 14.2 μmol·L⁻¹, two folds higher than its positive control MOX.  But there were no significant effects on channel kinetics.  In addition, the inhibitory effect of CFX on HERG was enhanced when cells were subjected to altered extracellular K⁺ concentration.