Combustion synthesis of Ti3SiC2/TiC composites from 3Ti/xSi/2C (x=1, 1.1, 1.2) powders was conducted under high-gravity conditions with gravity up to 895 G. The results showed that the phase composition of the products strongly depended on the gravity level. We find that high-gravity synthesis favors the growth of TiC phase over Ti3SiC2 phase, as a consequence of the reduced existence time of the Ti-Si liquid phase. This discovery suggests that gravity provides a new leverage for controlling product phase composition in combustion synthesis. It was also found that the densification process during combustion synthesis could be enhanced under a high-gravity condition.