Abstract: The paper presents the thermal and deformation analysis of electron gun cathode for Gyro-TWT using the finite element analysis software ANSYS, which obtains the temperature distribution and thermal deformation of the cathode model. In order to maintain the uniformity of surface temperature of the cathode emitter, the contact area of the thermal conductive medium with the emitter bottom is extended and the amount of the heater coil near the top of the emitter is reduced, the temperature difference decreases from 18 ℃ to 0.9 ℃. On the basis of the thermal analysis, thermal deformation analysis is demonstrated and the velocity ratio, longitudinal and transverse velocity spread, guide center radius all increase in EGUN code simulation.