This study investigates the change of the temperature and mechanical properties of the braking disk for the railway vehicle. The average temperature is measured about $100^{circ}C$ and the maximum temperature is measured over $200^{circ}C$ by non-contact sensor from Seoul to Chun-an. As a result of measuring, we determine the temperature of test(tensile and J-integral) at $20^{circ}C,;100^{circ}C,;200^{circ}C$ and $300^{circ}C$. In the test, the material values are decreased by the increasing of the temperature. But ratio of decreasing is the largest at $200^{circ}C$, the tensile test value is decreased about $10\%$ and the J-integral test value is decreased $30\%$. The mechanical properties of this material are mostly changed at $200^{circ}C$.