From the dynamic simulation of CNC machine, the motion trail of tool can be acquired and the layout types of CNC machine can be estimated. The visible optimization design is combined with conceptual design and the visible design flow of CNC machine based on conceptual design is put forward. Taking a five-axis CNC milling machine as object, the whole structure design is predicted by proposed conceptual design flow and three different design proposals are proposed. The motion trail of tool can be got by kinematics simulation of each proposal with ADAMS, from which the optimal proposal of the layout of the five-axis CNC milling machine is obtained and the feasibility of visual design combined with conceptual design is proved.