The mechanical properties and fracture toughness of permanent mold cast austempered gray cast iron(AGI) were compared to those of sand cast AGI. The iron was melted to eutectic composition in order to get better castability especially in permanent mold casting. Specimens prepared for tensile, impact and fracture toughness test were austenitized at 900℃ and austempered at 270℃ and 370℃ for 1hour. The strength, impact and fracture toughness of permanent mold cast AGI were found to be superior to those of sand cast AGI. The maximum value of 836㎫ in tensile strength, was obtained at the austempering temperature of 270℃. But ductility of AGI was not improved by permanent mold casting.