A method for joining Al2O3 ceramics has been investigated by utilizing NiO-Al volume combustion under various pre-heating gradients in air; the ignition temperature of the system has been made clear by changing starting composition, particle size of Al, and packing density of reaction powder compacts to optimize the conditions for ceramics joining. Combustion synthesized joining layers were mainly composed of NiAl2O4, Ni, and NiO. In order to prevent Al2O3 plates cracking during the combustion process, Al2O3 paste containing Al2O3 and water glass were deposited onto the Al2O3 surface, which formed intermediate layer joining the reactant layer and Al2O3 ceramics and decreased the temperature gradient between the two layers.