The invention discloses a diffusion method for preparing an emitting electrode of a polycrystalline silicon solar battery. The diffusion method comprises the following steps: mainly adopting a liquid-state POCl3 phosphorus source and using a high-concentration doped diffusion technology to achieve the purpose of improving the silicon battery performance by improving a phosphorus distribution curve of the emitting electrode. A multiple through-source diffusion method comprises the following steps: after carrying out preoxidation on a silicon wafer, first active diffusion is carried out on the silicon wafer at a lower temperature; and then second active diffusion is carried out at a high temperature; or third active diffusion is carried out at a higher temperature. Compared with the primary active diffusion, the method can improve the efficiency in the condition that the cost is not increased.