The invention belongs to the field of auxiliary power maintenance equipment, and specifically relates to a portable step voltage early-warning apparatus which comprises detection electrodes disposed on front and rear ends of an insulated shoe and a circuit board for arranging a voltage acquisition circuit, wherein the detection electrodes are electrically connected with the circuit board, and the circuit board is arranged in an apparatus housing. A voltmeter and a processor in communication connection with the voltmeter are arranged in the apparatus housing, an alarming horn for giving off an alarm is arranged on the external surface of the apparatus housing, and a band for binding the apparatus housing on a leg is arranged on the external surface of the apparatus housing. The portable step voltage early-warning apparatus is disposed on one insulated shoe of a worker, which changes conventional bi-feet prediction method, measures step voltage earlier, and ensures life safety of the worker. The apparatus is small, portable, convenient and rapid, and can be used only by sleeving on a foot. The apparatus is worthy of wide promotion.