The invention discloses a method and a device for carrying out ECG lead-off detection. A lead-off threshold range is first set; any signal in each ECG lead channel is acquired one by one, and the acquired signals are switched and outputted every 50mS to 200mS; peak detection is carried out on the outputted signals, and if the signals are direct-current signals, the signals are directly outputted after peak detection; if the signals are power frequency interference signals containing direct-current components, the peak values of the signals are detected; and if the peak values exceed the lead-off threshold range, ECG leads come off, or else, the ECG leads do not come off. Since the invention adopts the method of peak detection to carry out ECG lead-off detection, the invention solves the problem that the software filtering in the conventional lead-off detection method can cause lead-off misjudgement when the operating environment of the equipment is poor. In a word, the invention has the advantages of low cost, high reliability, low requirements on device parameters and the like, and brings more convenience to application.