Laser beam automatic alignment systems are used to align the SG-Ⅲ prototype facility laser. Considering the facility qequirement, combining the key technique of automatic alignment, according to the image relay of the pinhole, utilizing the optical position and the spatial location of the four pinholes of the main spatial filter in the four-pass beam in the SG-Ⅲ, this paper presents a reasonable scheme for automatic aligning in the four-pass amplifier, which has been fully checked on the multi-pass amplifier experiment system.The centering sensitivities of the system are less than 0.5% of the beam diameter. The pointing sensitivities of the system are less than 10μm.