Abstract: In the paper the effect of addition of A12O3 and SiO2 powders on the grain size of UO2 pellets is studied. The results show that the doping with small amount of A12 O3 and SiO2 powders can promote grain growth during sintering, but an excess of additive leads to suppression of pellet densification, when the sum of A12O3 and SiO2 powders is constant the different proportion of additives can also effect the grain size of UO2 pellets after sintering, when only the SiO2 powders are added, the grain size of UO2 pellets hardly changes, but with increasing of A12O3 powders, the grain size of UO2 pellets grows up, the liquid phases form along the grain boundary during sintering due to doping with A12O3 and SiO2 powders, which enhances the grain growth.