Density, purity, grain, and grain size distribution are the key factors that influence the transparency of an optical ceramics. To achieve high transmittance, efforts should be made to eliminate or minimize scattering or absorption of light. The aim of this paper is to verify the effect of two-step sintering technique for translucent alumina. The density and transmittance of the samples were enhanced by pre-heat treating at 800°C for 50 hours before the high temperature sintering. Abnormal grain growth was successfully suppressed by a two-step sintering technique and a small amount of MgO as additives. It is a very effective technique for designing homogeneous microstructure and high transparency in high purity alumina.