Abstract: Due to the advantages of high efficiency，wide speed range，high torque density and great control

performance，permanent magnet synchronous motors（PMSM）have been widely used in driving systems of electric vehicles（EVs）. However，as the increase of power density，the problem of temperature rise caused by loss heating has become one of the development limitation of PMSM for EVs. High temperature rise will damage the components of motors，shorten the life span of motors and reduce the reliability of electric driving system. In order to ensure the stable and reliable operation of PMSM，the investigation of motor temperature filed is of great significance. By reviewing the present research papers，the key issues in temperature field investigation of PMSM，including the source and calculation methods of power losses，the paths and forms of heat transfer，the temperature file distribution laws，and the temperature file modeling and experimental technique were summarized. Meanwhile，the challenges and problems in each aspect were summarized. Finally，the key problems urging to be solved in the temperature filed investigation of PMSMin EVs were pointed out.

      Key words: permanent magnet synchronous motors（PMSM）；loss calculation；heat transfer path；thermal

model；experimental technique