Under the frequent peaking operation of water-hydrogen-hydrogen cooled turbo-generator, the temperature of the rotor winding changes repeatedly for a long time and is subjected to thermal stress, which leads to deformation of winding and inter-turn insulation, and directly affects the performance and stability of the generator, so it is very important to study the temperature distribution law and the thermal deformation law of the rotor winding under the variable operating conditions. A 600 MW water-hydrogen-hydrogen cooled turbo-generator is taken as the object of study, according to the rotor structure, the calculation area under the rotating state is determined, and a three-dimensional electric-heat-fluid coupling calculation model is established. Under the corresponding basic assumptions and boundary conditions, the temperature field and fluid field distribution of the rotor are calculated, and the accuracy of the simulation calculations is verified by comparing the measured results. The results of the rotor temperature field are taken as thermal loads, and the corresponding boundary conditions are added to calculate the thermal deformation of the rotor winding under variable operating conditions, and the thermal deformation law is further summarized.