The tribological properties of alumina ceramics in unlubricated sliding contact were investigated using a pin on disk test machine under controlled temperature and normal load. The tribological behaviour can be classifled into two groups as follows : (1) At low and high temperature, T<300°C and 800°C<T, wear surface becomes smooth by formation of tribo-film. Friction coefficient or specific wear amounts is less than 0.7 or 10-6mm3/Nm, respectively. (2) At middle temperatures, 300°C<T<800°C, wear surface becomes relatively rough due to brittle fracture. Friction coefficient and specific wear amount show high values. These behaviours are summarized as wear diagram with temperature and normal loadaxes. Furthermore, it is analysed experimentally that formation and preservation of smooth tribo-film on wear surface reduce the wear volume.