The thermal-stress fatigue characteristics of C / V graphite cast iron produced by reduced-Mg method was investigated by thermal cycling consisted of heating to 700℃ in fluidized bed containing alumina particles (ø297-420㎛) as heat-transfer medium and water-cooling to 25℃. And the effect of graphite morphology on thermal-stress fatigue resistance was investigated by repeated thermal cycling with regard to crack initiation and propagation. It was reported that C / V graphite cast iron would have high thermal-stress fatigue resistance due to its superior thermal conductivity to the nodular graphite cast iron and strength to the flake graphite cast iron. In this study thermal-stress fatigue resistance was high in nodular, C / V and flake graphite cast iron in the order. The graphite morphology was considered to effect both thermal stress and strength. The thermal stresses developed were 19.8㎏/㎟ in C / V graphite cast iron, 15.2㎏/㎟ in flake graphite cast iron and 30.2㎏/㎟ in nodular graphite cast iron. The spacings between graphites were 0.101㎜ in C / V graphite cast iron, 0.152㎜ in nodular graphite cast iron and 0.074㎜ in flake graphite cast iron. Nodular graphite cast iron which had longer spacing between graphites and smaller stress concentration than C / V graphite cast iron was superior to C / V graphite cast iron in resistance to thermal-stress fatigue. Dominant effect for it was strength.