Abstract: With the increase of new energy generation and the development of auxiliary peak regulation task, the pressure of coal-fired thermal power units to undertake the power grid regulation task is increasing. First of all, this article taking Huaneng Power plant 2 * 600 mw supercritical thermal power generating unit as the research object, analyzes the current depth of the frequent load of generator stator and rotor, the influence of the main problems are caused by copper iron expansion difference and temperature difference generator winding of loose deformation, rising vibration of the generator, generator oil, It is pointed out that thermal stress and thermal deformation caused by peak load balancing are easy to be ignored and should be paid more attention to. Then, the thermal stress and thermal expansion difference between stator and rotor during frequent deep peak-adjustment are calculated and analyzed in combination with the peak adjustment parameters of No. 5 generator in Shangan Power Plant, and it is verified that the current deep adjustment mode will not cause plastic deformation of windings in accordance with the requirements of generator technical standards. Finally, through field tests, the effects of changing hydrogen temperature and pressure on thermal stress and thermal expansion difference of generator and rotor are analyzed, and the optimization measures and matters for attention under frequent peak regulation operation mode of generator are put forward, which provides useful reference for flexibility transformation of generator set.