The invention discloses a diffusion technology for reducing dark current of a metallurgical silicon solar battery, which includes the steps of firstly, carrying out concentrated phosphorus diffusion at the low temperature: feeding from a high-concentration phosphorus source for diffusion at the low temperature so as to form high-concentration phosphor doping; secondly, performing phosphorus gettering for a long time at the high temperature: releasing impurities such as deposited impurities, displacement impurities or other impurity complexes of iron, carbon, boron, oxygen and the like into interstitial impurities at the high temperature, so that the interstitial impurities quickly release into a phosphorosilicate glass layer with high solid solubility, high-temperature phosphorus gettering is completed, and the minority carrier lifetime of a body is prolonged; and thirdly, propelling at the lower temperature: at the lower temperature, propelling the junction depth, adjusting to square resistance meeting technological requirements, and lowering the solid solubility of the impurities in a surface concentrated area along with the temperature, so that the interstitial impurities turn to the deposited impurities, the complex impurities and the like. A metallurgical crystal silicon wafer is diffused by means of the diffusion technology, so that the dark current of the solar battery can be effectively reduced, and the conversion efficiency of the solar battery is improved.