Transparent ceramic materials have excellent strength, hardness and optical properties, which have important application prospect in light-weight transparent protective armor. However, the preparation of transparent ceramic components with large protection area and high transmittance properties is the main challenge to achieve application. In this work, large-size yttrium aluminum garnet (Y₃Al₅O₁₂, abbreviated as YAG) transparent ceramics with low deformation and excellent optical quality were fabricated by reactive sintering in vacuum using domestic high-purity Al₂O₃ and Y₂O₃ powders as starting materials, and the key technologies including dry pressing, calcining, high-temperature vacuum sintering and optical performance were broken through. In addition, as the upgrading of molding and sintering equipment, the dimension of YAG transparent ceramic was enlarged to 1040 mm×810 mm×15 mm, laying a substantial foundation for future applications.