In the process of high speed milling of titanium alloy, the milling temperature change had an adverse effect on machining accuracy, machining surface integrity and machining efficiency. To deal with this problem, heat conduction mode, the heat convection between cutting tools and air medium, and heat flux intensity boundary conditions in actual milling process are fully considered. And according to general heat equation, the heat conduction model of transient temperature field is built. The differential form of temperature field model are converted into corresponding form of the integral functional equation by the weighted residual method. A certain accuracy method for calculating the approximate solution is presented. And the transient temperature response of space element in milling system is obtained under equal time intervals. Finally it is proved that the model is correct by experiment result, which laid a solid foundation for accurately analyzing milling temperature.