MgAl2O4 transparent ceramic is a superior mid-infrared material, which is widely used in military and civil fields. In this paper, the effect of sintering process on the phase, microstructure and optical properties of magnesia alumina spinel transparent ceramics was investigated, and the sintering process route suitable for high-quality magnesia alumina spinel transparent ceramics was determined, which is of great significance for accelerating the industrialization of large-scale transparent ceramic armor materials. The results show that Li ions in hot pressed (HP) MgAl2O4 transparent ceramics may exist in the form of LiAlO2. The preferential growth surface of MgAl2O4 transparent ceramics obtained by hot isostatic pressing (HIP) sintering process is (311). Al and Mg ions of MgAl2O4 ceramics prepared by HP and HIP sintering deviate from the stoichiometric ratio, and Al/Mg ratio is greater than 2. The small grains in the ceramics increase with the increase of HIP pressure, and the grain size of MgAl2O4 ceramics is within 20-40 μm, which is conducive to improving the average transmittance of 3-5 μm. Based on the results by hot isostatic pressing test, the HIP sintering temperature of 1 750 ℃ and the pressure of 170 MPa are conducive to improving the average infrared transmittance (>85 %). In addition, the HIP sintering time has little effect on improving the infrared transmittance of MgAl2O4 transparent ceramics.