Traction motor of electric vehicle is required high torque and high output density. So, relatively large current is applied. When a large current is applied, large heat is generated. At this time, the heat of the stator rises above 140 t. This value is a high value which is characteristic of the electric motor can be greatly changed. In general, if the electric motor production is complete, control is tuned for optimal operation. The tuning control value is not considered according to temperature rise. In this paper, when the interior permanent magnet synchronous motor (IPMSM) of electric vehicle is driven, a characteristic change due to temperature rise of the IPMSM is studied by mathematically. In addition, it has proven results by using Finite Elements Method (FEM) analysis.