The structure and adhesion of an alumina coating an a ceramic substrate with NiCrAlY alloy bond coating was investigated by heating at 1573 and 1673 K in the air, Phases of NiO, NiCrO3, NiAl2O4, CrAl2O3, and Ni were revealed in a 100 mu m thick bond coating on heating at 1573 and 1673 K. A veined structure was also detected in the coating heated at 1573 K. The adhesion strength of the coating was improved and reached approximately 20 MPa on healing ar 1573 and 1673 K for 14.4 ks in air although the strength of the as-sprayed coating was only 2 MPa. The improvement of adhesion strength may arise from the formation of NiAl2O4 with a spinel structure at the interfaces of the top coating/bond coating/substrate coating system. The adhesion strength of fine coating improved on decreasing the bond coating thickness and reached approximately 45 MPa for a 20 mu m thick bond coating which was heated at 1673 K. Only NiAl2O4 oxide was formed in the bond coating.