Effect of quenching medium on the mechanical properties of ductil iron GCD 50 has been investigated using ADI treated specimens. The specimens have been austenitized at $900^{circ}C$ for 2 hours, followed by controlled cooling to $800^{circ}C$ under the cooling rate of $0.05^{circ}C/sec$, then austempered at $380^{circ}C$, $330^{circ}C$, $280^{circ}C$ and $230^{circ}C$ for 1 hour. The specimens treated in the salt of 5% water were found to have higher tensile strength than that of the normal salt bath. Elongation and impact energy increased in proportion to the increase of retained austenite volume fraction. The increase of cooling rate of the salt by the addition of 5% water to the salt resulted in the increase of retained austenite volume fraction and the formation of fine bainitic ferrite.