A numerical analysis model of friction stir welding was suggested by the direct interface area calculation method aided for axisymmetrically and non-axisymmetrically shaped tools. A general moving object was used to represent the tool movement based on the commercial CFD software. The plunging and welding processes were performed in the Eulerian description. Based on energy conservation laws, the torque induced power input, interface friction heat, and plastic deformation heat were modeled and evaluated. The measured temperature and torque were compared with the calculated results. The results of the combined error mode showed the conditionally acceptable results. The proposed model could be used for the torque and temperature prediction with a relatively short calculation time.