Abstract: The canned primary pump motor which is mainly used to carry the fluid of high temperature,high pressure,radioactive,toxicity and causticity,it plays an important part in chemical plants and nuclear power stations.Therefore its safe and steady operation is very important to the loop system.Basing the complex of heating and cooling and the specialty of high temperature and air proof conditions,a physical model of three dimensional temperature coupled field for a 5 000 kW large canned motor of the primary pump was established in this paper.During the delivery test,abnormal temperature occurred in the finger plate.The temperature of the finger plate and the cone ring was calculated using the finite volume method.Calculation results revealed the cause.Thus the configuration was modified.A new connecting scheme of finger plates with insulation and the cone ring was provided.The overheat problem at the motor’s end was resolved.Furthermore,the theory and practice basis will be provided for cooling structure design and temperature calculation accurately of canned primary pump motors of larger capacity.