The invention discloses a method for preparing a backside-polished PERC battery. The method comprises: (1), depositing a single-sided protective film on the backside of a silicon wafer; (2) carrying out texturing on the silicon wafer plated with the single-sided protective film and removing the single-sided protective film of the silicon wafer during a pickling process after texturing; (3), carrying out diffusion on the single-sided-textured silicon wafer; (4), carrying out conventional secondary cleaning; and (5), depositing aluminium oxide/silicon nitride laminated passivation film at the back side, carrying out laser grooving, screen printing and sintering, thereby obtaining a backside-polished PERC battery. According to the method disclosed by the invention, the volume production threshold is low; the operation cost is low; micro-nano flatness is realized; and the photoelectric conversion of the battery is improved.