A three-dimensional finite element model of helix double-edge cutting is developed to study the ending milling process of titanium alloy Ti6Al4V. Several mechanics models of milling process, such as material constitutive model, friction model and heat transfer model, are implemented to improve finite element simulating accuracy. A milling force experiment is carried out, and a good agreement between simulation and experimental value is achieved, which proved that the finite element model presented in this paper is correct. Using this finite element model, chip formation and cutting temperature are simulated and analyzed. This work will be a base for process parameter optimization, tool’s optimization selection and design during high speed milling of difficult-to-cut titanium alloy.