The invention provides a pouring system for a permanent mold gravity casting aluminum piston, comprising a pouring cup, a vertical pouring gate, a horizontal pouring gate and an internal pouring gate, wherein a top end of the vertical pouring gate is communicated with an outlet of the pouring cup and the vertical pouring gate extends vertically; the horizontal pouring gate is communicated with a bottom end of the vertical pouring gate and extends horizontally; an inlet of the internal pouring gate is communicated with an outlet of the horizontal pouring gate and an outlet of the internal pouring gate is communicatied with a mold cavity of a piston mold; and cross sectional areas of the vertical pouring gate, the horizontal pouring gate and the internal pouring gate are increased in order. The minimum cross sectional areas of the vertical pouring gate, the horizontal pouring gate and the internal pouring gate in the pouring system are increased in order, so the pouring gate proportion of the vertical pouring gate, the horizontal pouring gate and the internal pouring gate is controlled strictly, and the pouring system becomes an open pouring system. Therefore, the mold filling speed of metal liquids at the outlet of the internal pouring gate can be reduced sufficiently to stabilize the mold filling process and the casting quality of an aluminum piston blank and decrease the defects of pinholes, slag inclusion, shrinkage porosity and the like of the piston blank, so that the process product yield of the piston blank can be improvd.