Numerical analysis was carried out to estimate transient temperature characteristic in friction welding of two similar materials of 6061 aluminum alloys. A method used in this study is a practical approach to combine a friction heat input model with a non-steady heat conduction analysis using a finite element method. In this analysis, data of aluminum alloy were used as material property such as specific heat, thermal conductivity. Experiments of friction welding were performed to examine the validity of calculated results. The measured values during the friction welding process were the fundamental characteristics such as rotation speed, pressure, torque and temperature. Transient temperature distribution was calculated using the friction pressure, the upset pressure and the rotation speed. The calculated results were compared with the experimental results about friction heat input and temperature characteristics. As a result, it was confirmed that estimation of transient temperature distribution in a whole friction process was practicable. In addition, it was feasible to simulate the transient friction heat input by incorporating a concept of time lag of first order into the friction heat input model. The maximum temperature distribution near the friction surface was useful in investigating the heat affected zone．
