The present invention provides a method for adjusting the mechanical error of an optical disc reading device. The optical disc reading device consists of a driving device and an optical pickup. The driving device has a base plate for supporting and rotating an optical disc. The method consists of moving the optical pickup to surface of optical disc, the optical pickup emitting two tracking light spots onto the surface, and the optical pickup reciprocally moving relative to the surface. Next, the optical pickup reads reflected signal of two tracking light spots for generating a track crossing signal. By using the track crossing signal, the method adjusts position of optical pickup relative to the base plate.