The effect of Yb2O3 addition on sintering of MgO ceramics was studied in this work. Increasing of Yb2O3 addition is helpful to densification and grain growth. The effect of Yb2O3 amount on densification decreased when the sintering temperature was increased from 1400°C to 1550°C. Quick densification and rapid grain boundary mobility in Yb2O3 doped samples come from the point defect because the dopant mainly located at the grain boundary, and this is meaningful for grain growth and densification. The results also illustrate that sintering time and sintering temperature would noticeably affect grain growth and densification process, which is not related to the amount of Yb2O3 addition.