The invention discloses a preparing method of a whole back electrode P type crystalline silicon heterojunction solar battery. The method comprises the steps that nanometer suede, a P+ type boron shallow diffusion crystalline silicon layer and an SiOx passivation/SiNx anti-reflection layer are prepared on the front surface of a P type silicon substrate; a P++ type boron heavy diffusion crystalline silicon layer is prepared on the back face of the P type silicon substrate, then printing corrosion slurry is used for achieving local corrosion on the P++ type boron heavy diffusion crystalline silicon layer, an intrinsic amorphous silicon membrane layer and an n type amorphous silicon membrane layer are subjected to deposition in sequence, and intrinsic and n type amorphous silicon on the surface layer of a P++ type boron heavy diffusion crystalline silicon layer zone is removed; then a transparent conducting membrane layer is subjected to sputtering, a P zone and an N zone on the back face of the P type silicon substrate are separated through laser; and finally electrode printing is carried out, and low-temperature sintering is carried out. According to the method, all metal electrodes are moved to the back face of the battery, electrodes are not arranged on a light-borne face, component production cost is lowered, battery composite loss is lowered, accordingly, optical loss and resistance are obviously lowered, and efficiency is greatly improved.