The potential transformer is an important measuring device in the power system, temperature is one of the main factors affecting the accuracy of its measurement. In order to analyse the temperature field distribution of voltage transforme and enhance the heat dissipation ability of potential transformer, the coupling of temperature field and fluid field are calculated and analyzed by ANSYS software and CFX software. this paper takes 10 kV electromagnetic potential transformer as the research object. A simplified simulation calculation model is established. The simulation is based on scanning and subdivision, and the air convection heat transfer was considered. Through simulation calculation, the cloud chart of the temperature distribution of the potential transformer and the location of hotspot temperature are obtained. The calculation results can provide basis for temperature correction and local temperature rise measurement. At last, the factors affecting the temperature characteristics are analyzed. The results show that, low voltage top winding is the most important part of voltage transformer, and is the key to temperature monitoring. And the thermal conductivity and viscosity of oil have little influence on the temperature field in normal temperature range, which can be ignored. The convective heat transfer coefficient of the side surface has a great influence on the hot spot temperature. The heat dissipation ability of the voltage transformer can be enhanced by increasing the heat transfer capacity of the side surface.