Two different filling systems of ZL101 pump casting were designed in this paper, and the flowing field, solidification phase field and distribution of shrinkage were calculated by the FEM numerical simulation. The results show that the melt alloy fills smoothly and the gas inside the resin sand core exhaust effectively from the riser by adjusting the bottom injection casting system, which forms the solidification sequence from top to bottom and from inside to outside. The average tensile strength, yield strength and elongation of the bulk samples are 334.5MPa, 274MPa and 5.8% after the T5 treatment process, which meets the technical requirements of HB962-2001 Type II castings.