<p>Chatter frequently occurs during the high-speed milling of thin-walled workpieces owing to their low rigidity and susceptibility to deformation. Based on a time-domain chatter model, this paper proposes a three-dimensional stability prediction method that incorporates dynamic characteristics and milling force coefficients. The modal parameters are extracted through an impact hammer test, and milling forces are calculated according to milling force coefficients. Using the statistical variance of displacement as a detection criterion, the three-dimensional stability lobe diagram is constructed with respect to spindle speed, axial depth of cut, and tool position. The effects of different milling parameters on milling stability are investigated, and the accuracy of the proposed method is verified by measuring the surface roughness of thin-walled workpieces. The results demonstrate that implementing a variable spindle speed strategy significantly enhances surface quality, while the feed per tooth has a minor effect. This study provides a theoretical foundation for stability analysis and process parameter optimization of thin-walled workpiece milling.</p>