In the high-pressure and high-temperature experiments with the diamond anvil cell and large volume press, metal powder (such as Pt, Au, Fe) is usually added for the purposes of pressure measurement, laser heating and mineral growth rate reduction. It is widely acknowledged that these metal additives should not react with the system under investigation. However, no enough attention has been paid to the issue whether or not these metal additives affect the reaction rate. Under appropriate p-T conditions, corundum and coesite combine to form kyanite. With the addition of different amounts of Pt powder into the system, we investigated the effect of adding Pt powder on the kyanite formation reaction. We found that adding Pt powder promotes the synthesizing reaction, and the promoting effect increases with the amount of added Pt powder. These results can provide important constraints in interpreting relevant high-pressure and high-temperature experiments.