Thermal and deformation analysis of W-band gyrotron traveling wave tube amplifier ( Gyro-TWTA) gun are carried out by using the finite element code ANSYS in the paper. Temperature distribution and thermal deformation of the cathode component at given heater power are simulated. These results are verified experimentally in an electron gun. The measured temperature distribution is in agreement with the simulation prediction.Finally, the electron trajectories with and without considering deformation are simulated by EGUN code.