Due to its excellent mechanical properties, high thermal conductivity, broad transmittance wavelength band, and good chemical stability, transparent yttrium aluminum garnet (Y3Al5O12, YAG) ceramics has become an important optical material since 1995. In this work, vacuum reactive sintering method is used to fabricate the transparent YAG ceramics. The effects of stoichiometry, sintering aids, and sintering conditions on microstructure and further the optical quality of the sintered ceramics have been investigated thoroughly by using XRD, SEM, TEM, and the optical spectroscopy methods. The post hot isostatic press is used to further remove the residue pores. High optical quality pure YAG and various rare earth ions doped YAG are developed successfully. Their application for optical windows, gain media for solid state lasers, protective covers for smart phones and etc. are demonstrated.