In a method for compensating step value of a processing product placed on a machining device using a computing device, a machining tool of the machining device is controlled to be moved to each benchmark point in sequence. Actual coordinate values of each benchmark point is calculated by a laser detection device of the machining device. The acquired actual coordinate values are fitted to be a benchmark plane. New coordinate values of each machining point in a machining program is acquired by rotating each of the machining points to the benchmark plane. The machining tool is controlled to move to each machining point according to the calculated new coordinate values and an actual z coordinate value of each machining point is acquired using the laser detection device. The step compensation value in Z-axis of the each machining point is calculated and transmitted to the machining device.