Abstract: Because STL (stereo lithography) file can transfer the information of solid model accurately,a method to compute solid radiation heat flux of spacecraft based on STL file was proposed. The boundary cells were identified according to topological relationship of cells and nodes and on that basis,radiation heat transfer was computed. Computation method of view factors and external heat flux of complicated structure based on STL file and finite element method was expatiated in detail. Coupled computation of conduct and radiation heat transfer with finite element method was researched. Finally,three-dimensional transient temperature field of key equipment of spacecraft in orbit was computed by finite element method (FEM).