Transparent polycrystalline yttria is a promising optical ceramics with excellent physical and chemical properties. A commercial yttria powder with a mean particle size of 1.0 μm and narrow size distribution was selected as the starting material. Transparent polycrystalline yttria ceramics without any additives were successfully prepared by hot isostatic pressing (HIP) at 1700 ℃ for 2 h under the pressure of 200 MPa in Ar following spark plasma sintering (SPS). The as-prepared specimens consist of uniform grains of ～40 μm. Scanning electron microscopy (SEM) images show their pore-free structure. The influences of the yttria powder and sintering process on the properties of the yttria ceramics, including the microstructure and optical properties, were further investigated in our study.