The Three Gorges 700 MW hydrogenerator was used as an example to establish a model of rotor magnetic pole. The thermal stress was solved by finite element method based on the theory of heat transfer and heat stress. Based on the relative basic assumptions and boundary conditions, the distribution of magnetic heat stress in case of winding interturn shortcircuit was given. On the basis of this calculation, the influence of the change of shortcircuit turns and the change of shortcircuit position on the magnetic heat stress was studied. Many meaningful conclusions have been obtained through computational research. The results lay the foundation for further study of the interturn shortcircuit, and provide some reference for the motor designers and related research work.