The influence of Zirconium on the grain refinement performance of Al-Ti-C master alloys and the effect mechanism has been studied in this paper. The experimental results show that Zr not only results in poisoning the Al-Ti-B master alloy, but also poisons the Al-Ti-C master alloys. The poisoning effect is more obvious at higher melting temperature. When 0.12%Zr is added into the melt, the grain refinement performance of Al-5Ti-0.4C refiner with 0.2% addition level absolutely disappears at 800 degrees C. The experimental results also show that it is difficult to refine the commercial purity Al containing 0.15%Zr by Al-5Ti-0.4C master alloy. Further experiments show that the Zr element can interact with both TiAl3 and TiC phases. If both of them are present, Zr preferentially reacts with TiAl3 phase.