NOVELTY - Diffusion of polycrystalline silicon solar photovoltaic battery silicon chip is performed by etching silicon chip in initial temperature of 780-820 degrees C with oxygen flow rate of 0.25-0.35 L/minute; heating tubular diffusion furnace to 820-850 degrees C, and continuing filling oxygen for oxidation with oxygen flow rate of 0.45-0.55 L/minute for 35-45 minutes; and controlling first phosphorus diffusion at 810-830 degrees C, introducing nitrogen at 0.87-0.93 L/minute, introducing oxygen at 0.45-0.55 L/minute, and performing first phosphorus diffusion for 5-15 minutes.    USE - Method for diffusion of polycrystalline silicon solar photovoltaic battery silicon chip (claimed).    ADVANTAGE - The method provides for excellent phosphorus impurity doping concentration distribution, strong controllability of diffusion rate, and improved yield of diffusion of silicon chip.    DETAILED DESCRIPTION - Diffusion of polycrystalline silicon solar photovoltaic battery silicon chip comprises:    (A) etching silicon chip in initial temperature of 780-820 degrees C with oxygen flow rate of 0.25-0.35 L/minute;    (B) heating tubular diffusion furnace to 820-850 degrees C, and continuing filling oxygen for oxidation with oxygen flow rate of 0.45-0.55 L/minute for 35-45 minutes;    (C) controlling first phosphorus diffusion at 810-830 degrees C, introducing nitrogen at 0.87-0.93 L/minute, introducing oxygen at 0.45-0.55 L/minute, and performing first phosphorus diffusion for 5-15 minutes;    (D) controlling first impurity distribution tubular diffusion furnace temperature at 840-870 degrees C, introducing oxygen at 0.45-0.55 L/minute and nitrogen at 9.3-9.7 L/minute, and removing impurity for 5-8 minutes;    (E) controlling second phosphorus diffusion at 840-890 degrees C, introducing nitrogen at 0.95-1.05 L/minute and oxygen at 0.45-0.55 L/minute, and carrying out second phosphorus diffusion for 8-20 minutes;    (F) controlling second impurity distribution tubular diffusion furnace temperature at 850-890 degrees C, introducing oxygen at 0.85-0.95 L/minute and oxygen at 9.5-10.5 L/minute, and removing impurity for 5 minute;    (G) controlling tubular diffusion furnace temperature at 500-800 degrees C, introducing nitrogen, and performing absorption for 50-70 minutes; and    (H) using silicon carbide in silica tube diffusion furnace for taking out silicon chip, and stopping introducing oxygen.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic view of polycrystalline silicon solar energy photovoltaic battery silicon chip diffusion.