Abstract: The effects of Sb on the microstructure of gravity casting ZL114A alloy in metal mold casting were studied by means of polarized light microscope, scanning electron microscope and transmission electron microscope.The results show that the size and morphology of primary α-Al grains remain unchanged after adding Sb to the alloy under the metal mold casting conditions, the volume fraction of eutectic phase (including eutectic α-Al and eutectic Si) decreases, the eutectic Si is modified, and the eutectic Si in as-cast alloy becomes shorter without obvious branching.The shorter the eutectic Si after heat treatment, the higher the degree of spheroidization.The modification mechanism is the increase of the nucleation cores of eutectic Si.