To clarify the dry friction and wear characteristics of spheroidal graphite cast iron under high sliding speed and high contact pressure, especially those in the state of thermal wear, the wear tests of sliding a cast iron pin on a mild steel disk were carried out by using the pin-on-disk type test rig. The variations of the friction force, the wear rate and the temperature rise with the sliding distance were experimentally measured and the relations among them were clarified. The friction and wear of spheroidal graphite cast iron pin are strongly influenced with the friction-induced tempera ture rise. Its wear rate changes in three steps as the increment of sliding distance because of the changes of its hardness by temperature rise (the first, the second and the third wear regions in order). The thermal conductivity and the hardness change by temperature rise of spheroidal graphite cast iron give the effects on thses three step changes of wear. Meanwhile, the coefficient of friction decreases in the first and the second wear regions as the sliding distance increases, and it finally converges to some constant value in the third wear region. From the experimental results, some empirical formulae giving the relations between the coefficient of friction and the wear rate versus the sliding conditions were derived.