Abstract: Normally buildings from start of construction to being put into use，their main structures have been under a state of sun exposure． In this process，the change in temperature will have an effect on the deformations and internal forces of the structures． Based on a prefabricated steel frame structure with inclined support joints，the unit activation and deactivation function of MIDAS Gen were used to simulate all of the actual construction processes，of which the extreme temperature difference of the sun surface and the back sun face was used to simulate the thermal effect and applied them to the model． Then it was contrasted the difference of considering temperature and without considering it，there were obvious differences in the internal force and deformation of the structural members，showing that it is necessary to consider the construction process according to actual conditions．