Abstract: Cordierite was prepared by solid reaction of raw materials including decomposed magnesite, industrial Al₂O₃ and SiO₂ powder. Adding different mass fractions of Eu₂O₃, Dy₂O₃ and Er₂O₃ as additive, the effect of Eu³⁺, Dy³⁺ and Er³⁺ on the composition, grain size, lattice parameters, crystallinity and microstructure of crystalline phases was studied and compared. The crystalline phases and microstructure were determined by XRD and SEM respectively. The lattice parameters and crystallinity of the crystalline phases were estimated by X'Pert plus software. The phase composition was evaluated by semi-quantification method, and the grain size was calculated by Scherrer formula. The results show that the mullite phase is observed in the sintered samples because of the addtion of Eu₂O₃, Dy₂O₃ and Er₂O₃. Due to the substitution of Eu³⁺, Dy³⁺ and Er³⁺ for Mg²⁺, the lattice parameters and lattice volume of cordierite are changed. The liquid phase and density for room temperature increase, while relative crystallinity and grain size of cordierite decrease with addtives increasing. Comprehensive analysis shows that the effect of Eu₂O₃ on the phasetransition is the weakest, while the effect of Eu₂O₃ is the strongest among the three additives. The effect of Eu₂O₃ on sintering property and thermal shock resistance is the best of three additives.