In the present work, the mechanical properties and erosion-resistance ability of hot-pressed and pressureless sintered slag α-sialon ceramics, which were started from slag α-sialon powders prepared by SHS technique based on slag powders, [J. Mater. Chem. 12 (2002) 1199] were measured. The hardness and toughness of pressureless sintered slag α-sialon samples reached 15.53 GPa and 4.72 MPam1/2 respectively. The strength of hot-pressed slag α-sialon ceramics reached 599 MPa as well. In comparison with Al2O3 and ZrO2 ceramics, as-sintered slag α-sialon ceramics showed much higher erosion-resistance ability. These properties are very close to that of normal α-sialon ceramics prepared by expensive chemical agents as raw materials. [Copyright &y& Elsevier]