The invention discloses a detection method and device for the minimum interelectrode clearance during numerical-control electrochemical machining. The method comprises the steps that a current monitoring module is observed, when the observed machining current tends to stable, machining is paused, a direct current power supply is turned off, and the position of a Z axis at the moment is recorded; an electrolyte in the machining clearance is blown away, so that a workpiece and a tool are in the dry state; a multimeter is connected to a measuring circuit and configured to be in the buzzing gear,then, a negative electrode is controlled to be fed downwards, when buzz is heard, a reading of the Z axis at the moment is recorded, and the interelectrode clearance during the machining is calculated; other machining parameters are kept constant, the negative electrode feeding speed is increased, the electrochemical machining process continues being completed, the interelectrode clearances at different feeding speeds are measured till stable machining cannot be conducted, then, measurement work is finished, and finally, the minimum interelectrode clearance during numerical-control electrochemical machining is obtained. According to the detection method and device, the detection device does not need to be additionally connected with a sensor, is easy to operate and implement and can detectthe minimum machining clearance, so that small clearance electrochemical machining is achieved, the electrochemical machining precision is improved.