The invention discloses a pre-alignment method of a silicon wafer. The pre-alignment method comprises the following steps of firstly, centering the silicon wafer by a centering platform, a lifting platform and a rotation platform so that the center of the silicon wafer is aligned to the center of the positioning platform; secondly, acquiring an image of the silicon wafer by image acquisition equipment; thirdly, dividing the image into a plurality of sub-regions from top to bottom by scribing grooves according to image characteristic; fourthly, processing the image, and acquiring a central axis of the scribing groove conforming to a set condition as a generalized mark; and finally, rotating the silicon wafer to complete direction according to a different value between the generalized mark and a designated on-chip angle. According to the surface characteristic of the silicon wafer in the acquired image, the image is divided into the plurality of sub-regions by the scribing grooves, the central axis of the scribing groove in the optimal level is acquired as the generalized mark, no extra mark is needed to be made on the silicon wafer, the influence of an external factor on the generalized mark is greatly reduced, high stability is achieved, and the recognition accuracy and the pre-alignment accuracy of the silicon wafer are improved.