Objective To investigate the anesthetics that do not interfere with electrocardiograms (ECG) bycomparing the effects of three anesthetics on ECG in C57BL/6 mice. Methods Mice were randomly divided into threegroups: intraperitoneal injection of 20% ethyl carbamate, 1% pentobarbital sodium, and 2. 5% chloral hydrate. Aftercomplete anesthesia, the mice were connected to an ECG scanner by a limb lead for 1 hour of electrocardiogram recording.Results Within the administration time between 0-40 min, 20% EC did not significantly affect the ECG parameters ofmice. However, mice in the 1% pentobarbital sodium group had a reduced heart rate, and prolonged PR interval and QRSduration. Mice in the 2. 5% chloral hydrate group had a reduced heart rate and prolonged PR interval. Conclusions Ourfindings indicates that 20% EC has the least effect on the ECG of C57BL/6 mice and that 2. 5% chloral hydrate is suitable for experimental studies 20 min after anesthesia is induced in mice.