Microstructure evolution of Zr and P compound modified Si/ZA27 composites during remelting at 475℃ was observed. The results show that microstructure of the composites modified by Zr and P is converted from developed dendrite into short-coarse dendrite with fine primary Si phase. The interconnected structure with a few or without boundaries is generated due to the growth of short-coarse dendrite, and is further formed irregular independent particle during eutectic phase melting, resulting in the spheroidization of the particles during partial remelting process. With the increase of heating time, the primary Si phase in the microstructure is spherodized with the decrease of Si phase size.