Mullite ceramics were fabricated by a reaction-bonding technique from the powder mixtures of Al 2 O 3 and Si with an Y 2 O 3 addition. The effects of the initial powder composition on the mullitization and densification behaviors were investigated. It has been shown that mullitization and densification can be simultaneously enhanced by a low-viscosity yttrious silicate glass. After a 2h heating at 1400 o C, all the specimens exhibited a dense microstructure. Moreover, mullite grains were observed to have an elongated morphology, while the yttrious silicate glass was found to crystallize into Y 2 Si 2 O 7 at the later stages of mullite growth.