In the process of milling thin-walled plate, chatter is one of the major limitations on productivity and part quality even for high speed and high precision milling machines. Therefore, it is necessary to avoid chatter with a suitable choice of cutting condition. This paper studies the dynamic stability models of milling the thin-walled plate by analyzing the geometrical relationship of cutting, and derives the mathematic expressions in theory. Moreover, this paper develops a three-dimensional lobes diagram of the spindle speed, the axial depth and the radial depth. Through the three-dimensional lobes, it is possible to choose the appropriate cutting parameters according to the dynamic behavior of the chatter system.