An origin positioning method for controlling lifting motion of a wafer boat comprises the steps that firstly, the wafer boat is controlled to move downwards at a set speed parameter, and the wafer boat is controlled immediately to be decelerated and stopped when an origin sensor detects that the origin sensor is just shielded by a wafer boat lifting mechanism; secondly, the wafer boat is controlled to start to move upwards at a smaller speed parameter, when an origin pulse rising edge is detected, Z-phase pulses are searched for, and the wafer boat is controlled to be decelerated and stopped after the Z-phase pluses are found. In addition, after the steps, the wafer boat is continuously controlled to move downwards at a slow speed, and the wafer boat is stopped immediately when the origin pulse rising edge is detected, or Z-phase pulses are searched for, and the wafer boat is decelerated and stopped or stopped immediately after the Z-phase pulses are found. The accuracy and the stability for returning to the origin are improved through the steps. Besides, different working conditions of a digital sensor are combined for use, so that reliability is improved, and the implementation mode is quite simple.