The utility model discloses a lead assembly of an electrocardiograph. The lead assembly comprises a lead wire, a tray and a dual-purpose suction ball, a plug of the lead wire is a banana plug or a contact pin; the dual-purpose suction ball comprises a middle assembly. The middle assembly comprises a shell and a connecting pipe. Connecting pipe penetrating shell, two ends of the connecting pipe areconnected with the suction ball and the metal cover; a wire coil is arranged in the cavity of the shell; the wire coil sleeves the outer side of the connecting pipe; a coil spring is arranged betweenthe wire coil and the connecting pipe; the outer side wall of the shell is fixedly connected with an interface matched with the plug; a wire outlet is formed in the outer side wall of the shell, thepatch connecting wire is wound on the wire coil and extends out of the wire outlet, the end, away from the wire coil, of the patch connecting wire is connected with the patch connector, a fixing protrusion matched with the patch connector is arranged on the outer side wall of the shell, and a wire clamping device is arranged on the outer side wall of the shell and located above the wire outlet. According to the utility model, flexible switching between the electrode suction ball and the electrode patch can be realized, cleanness of the electrode suction ball is ensured, and stable contact of acquired signals is maintained.