NOVELTY - Phosphorus diffusion method of polycrystalline silicon solar battery, comprises: (a) developing a phosphorus-containing dopant on the whole front surface of the to-be-processed polycrystalline silicon chip; (b) placing the silicon chip in a diffusion furnace, raising the temperature, and simultaneously pumping phosphorus source gas, oxygen and nitrogen; (c) maintaining temperature, adding phosphorus source gas, dry oxygen and nitrogen, and allowing to diffuse; (d) cooling, and simultaneously passing oxygen and nitrogen; and (e) cooling, and discharging to finish diffusion process.    USE - The method is useful for phosphorus diffusion of polycrystalline silicon solar battery.    ADVANTAGE - The method adopts the development of phosphorus-containing dopant on the whole front surface of the chip to achieve gettering and remove the red edge of the polycrystalline silicon chip; and ensures photoelectric conversion efficiency of the battery chip improved upto 0.2%, and unexpected technical effect in comparison with the existing phosphorus diffusion method.    DETAILED DESCRIPTION - Phosphorus diffusion method of polycrystalline silicon solar battery, comprises: (a) developing a phosphorus-containing dopant on the whole front surface of the to-be-processed polycrystalline silicon chip; (b) placing the silicon chip in a diffusion furnace, raising the temperature to 880-930 degrees C at the heating rate of 1-10 degrees C/minute, simultaneously pumping phosphorus source gas, dry oxygen and nitrogen, where the phosphorus source gas flow rate is 0-2 l/minute, the flow rate of the dry oxygen is 0.5-2 l/minute and the nitrogen flow rate is 10-30 l/minute; (c) maintaining the temperature in the step (b), adding the phosphorus source gas, dry oxygen and nitrogen, allowing to diffuse for 20-50 minutes, where the phosphorus source gas flow rate is 0-2 l/minute, the flow rate of the dry oxygen is 0.5-2 l/minute and the nitrogen flow rate is 10-30 l/minute; (d) cooling to 800-850 degrees C at the cooling speed of 1-10 degrees C/minute, simultaneously passing oxygen and nitrogen, where the oxygen flow rate of is 1-10 l/minute and the nitrogen flow rate is 10-30 l/minute; and (e) cooling, and discharging to finish the diffusion process. An INDEPENDENT CLAIM is also included for the polycrystalline silicon chip, prepared by the above mentioned method.