Uniform Er3Al5O12 spheres are of great value for fabricating optical ceramics. The highly monodisperse and size-controllable erbium aluminum garnet (EAG) precursors for transparent ceramics were successfully synthesized through a new microwave process. The precursors constituted of ultrafine particles joining together by a hydroxyls formed compact network structure in the absence of SO42-, however, the morphologies of the precursors exhibited spheres with trace amount of SO42-. With manipulated programming of microwave irradiation parameters, narrow distributed particles of 40-50 nm were finally obtained by a separation of nucleation and nanocrystal growth. The mechanism behind the influence of microwave irradiation parameters on the growth of EAG precursors was preliminarily analysed. Easily dispersible and pure phase EAG were obtained at 950 ℃. The as-prepared EAG powders were used to fabricate transparent ceramics and transparent polycrystalline EAG ceramics were obtained under hydrogen furnace at 1750 ℃ for 8 h. The highly monodisperse and size-controllable erbium aluminum garnet (EAG) precursors for transparent ceramics were successfully synthesized through a new microwave process. The precursors composed of ultrafine particles together together by a hydroxyls formed compact network structure in the absence of SO42-, however, the morphologies of the precursors exhibited spheres with trace amount of SO42-. With manipulated programming of microwave irradiation parameters, narrow distributed particles of 40-50 nm were finally obtained by a separation of nucleation The mechanism behind the influence of microwave irradiation parameters on the growth of EAG precursors was preliminarily analyzed. Easily dispersible and pure phase EAG were obtained at 950 ° C. The as-prepared EAG powders were used to fabricate transparent ceramics and transparent polycrystalline EAG ceramics was obtained under hy drogen furnace at 1750 ℃ ​​for 8 h.