Effects of the sintering additives CeO2 and K2O on eliminating interphases of cristobalite and spinel were studied by means of XRD, SEM/energy-dispersive spectrometer, and TMA techniques to obtain high cordierite contents. Adding 4 wt% CeO2 significantly stimulates the conversion of cristobalite to cordierite, depresses spinel formation and yields less glassy phase. It is helpful to prepare a ceramic with a high content of cordierite and a low thermal expansion coefficient when sintered at 1400° C for 3 h. Addition of 1-2 wt% K2O results in a large amount of glassy phase and is less effective in eliminating the interphases.