Abstract: Aluminum alloy parts are usually processed by milling, and the milling parameters have an important impact on the product quality. In this paper, a time-varying model of milling cutter speed is proposed to analyze the influence of time-varying of milling cutter on aluminum alloy milling. Firstly, the time-varying model of milling cutter speed is constructed by MATLAB programming. Then the time-varying speed is introduced into the 3D aluminum alloy milling model established by finite element method. Finally, a three-dimensional model of aluminum alloy milling considering the time-varying of milling cutter speed is established, and the influence of the milling cutter's time-varying on aluminum alloy milling is analyzed. It is found that the time-varying of milling cutter speed will lead to a large dynamic change of the cutter's reaction torque and the maximum milling stress produced by the workpiece. Thus the stability of cutter speed should be ensured in the actual processing.