The invention discloses a method for manufacturing a silicon solar cell. In the process of manufacturing a PN junction on a silicon wafer, a selective diffusion technology method is adopted, i,e. laser is utilized to heat a position, on which a positive electrode intends to be manufactured, on the surface of the silicon wafer; and under the action of heating, phosphorus in a phosphorus source uniformly adhered on the surface diffuses towards the inner of the silicon wafer, thus a heavy doping zone with smaller sheet resistance is formed at the position on which the positive electrode intends to be manufactured to effectively reduce the sheet resistance of the silicon solar cell, thereby not only being beneficial for increasing the open-circuit voltage of the silicon solar cell; the increase of the open-circuit voltage effectively improves the conversion efficiency of the silicon solar cell, reduces ohmic contact of a metal electrode and the silicon solar cell, thereby reducing the series resistance of the silicon solar cell, and being capable of meeting the demand of industrialized production better.