The mechanical properties and fatigue crack growth rate fracture toughness of permanent mould cast austempered gray cast iron(AGI) were compared to those of sand cast AGI. Specimens prepared for tensile, impact and fatigue test were austenitized at $900^{circ}C$ and austempered at $270^{circ}C$, $320^{circ}C$, $370^{circ}C$ and $420^{circ}C$ for 1 hour. The strength, impact and fatigue crack propagation behavior of permanent mold cast AGI were found to be superior to those of sand cast AGI. Maximum values in tensile strength, BHN, Charpy impact energy, were obtained at the austempering temperature of $270^{circ}C$. Samely, the slowest fatigue crack growth rate was appeared at the austempering temperature of $270^{circ}C$. But ductility of AGI was not improved by permanent mould casting.