Abstract: Based on the principle of friction work,a numerical model of the heat input in the process of friction stir welding was established.The distribution of the transient temperature field and the temperature variable curve of feature points in the welding process of TC4 titanium alloy plate (4 mm) were accurately simulated by the FEA software of ANSYS.Results show that the distribution of temperature field is an ellipse with smaller front and bigger back in the welding process of TC4 titanium alloy,and the temperature peak is under the melting point when it was quasi steady-state.