Induction motor in place of DC one has been applied widely for DC electric rolling stock, because of the advantage of its utility and efficiency. However, further improvement of motor characteristics is crucial in order to realize environment-friendly DC railway system in the future. It is important to study more efficient machine; applying DC electric rolling stock for the next generation high performance system. Therefore, we have carried out fundamental study on reduction of energy consumption for electrified railway system with the aid of high temperature superconductor (HTS) technology. We have firstly tried to obtain the specification of HTS induction/synchronous motor (HTS-ISM), which is target HTS motor for the aforementioned purpose. Furthermore, we have investigated the relationship between the current transport property of HTS tape conductors and the torque characteristics of HTS-ISM. As the result, we have shown the possibility of the next generation DC electrified railway system with the use of HTS-ISM.