Based on the linear growth law of heating power during non-steady-state friction plug welding,the linearization of heat generation is carried out,and the heating model of friction plug welding under non-steady state is established. The finite element analysis software ABAQUS was used to establish a three-dimensional finite element model of friction plug welding in the unsteady state of 2 mm thick 7075-T6 aluminum alloy plate,and the accuracy was verified by the test results. The simulation results are in good agreement with the experimental measurements,and the error is within the allowable range,which verifies the correctness of the heat generation model and the numerical simulation results. The numerical simulation results show that the temperature and stress at any point close to the welding area are only related to the distance from the center of the plug hole.