The invention discloses a traveling-
wave tube internal temperature soft-measurement method based on a finite 
element model. With multi-point temperature values of the shell of a traveling-
wave tube as auxiliary variables, the finite element soft-measurement 
thermal model of the traveling-
wave tube is created; with heat source distribution as independent variables, a target function of an error sum of squares between the multi-point 
temperature measurement values of the shell and corresponding point temperature 
simulation values of the finite element 
thermal model of the traveling-wave tube is derived, and is solved by an iterative 
algorithm, so that an optimal heat source distribution solution is obtained, finally, the optimal heat source distribution solution is loaded into the finite element 
thermal model of the traveling-wave tube, and an 
internal temperature soft-measurement value of the traveling-wave tube is obtained by finite element stimulation calculation. The traveling-wave tube 
internal temperature soft-measurement method based on the finite 
element model breaks through the limitation of conventional detection, and prevents a series of 
complex problems brought about by temperature sensors placed in traveling-wave tubes, measurement is convenient, the implementation cost is low, and the traveling-wave tube internal temperature soft-measurement method based on the finite 
element model can be applied in the 
mass testing of traveling-wave tubes.