The invention relates to a preparation method of an N-type double-sided battery. The method comprises the following steps of (1) texturing; (2) boron and phosphorus co-diffusion at front and back sides of a textured silicon wafer by adopting a spin-coating method; (3) HF cleaning; (4) PECVD of AlOx and a passivation film at the front side; (5) the passivation film is deposited at the back side bymeans of PECVD; (6) screen printing and sintering; (7) laser edge isolation; and (8) light-heat treatment of the battery. According to the preparation method, the problem of boron and phosphorus diffusion at present is solved, the technological process is effectively simplified, cross contamination of boron and phosphorus elements is avoided and the conversion efficiency of the battery is improved.