In order to improve the service life of the electroplating alumina film / Al-alloy substrate systems, it is necessary to know their whole mechanical characteristics. Therefore, the special thermal residual stress specimen and depositing fixtures were prepared, respectively. Alumina films of 10 ~ 60 μm thickness were prepared by a positive pole oxidized technology in the sulfuric acid electroplating solution. The thermal residual stress of electroplating alumina films were measured by curvature method. and the relationship between thickness and residual stress of alumina films was also analyzed. It concluded that the residual stresses of electroplating hard alumina films were relatively small and tensile stress corresponding to 10 ~ 60 μm thickness, and the residual stresses decreased linearly with increasing thickness.