Abstract: Taking the GLU28×40 series CNC gantry milling machine as the research object, this study focuses on the typical problems of low-speed crawling and fluctuation of commutation consistency in the feed axis, and conducts research on friction characteristic identification and compensation tuning of the feed system. On-site identification is carried out using ISO 230-2 laser interferometry and VDI 3441 statistical indicators. A friction compensation and parameter optimization path constrained by the convergence of backlash deviation, non-deterioration of repeat positioning accuracy, and improvement of consistency in trial-cutting dimensional deviation is proposed, and a repeatable closed loop is formed by friction compensation and servo parameter tuning. After compensation and tuning, the flatness of the trial-cut workpiece is improved from 0.0214 mm to 0.0013 mm, which verifies the contribution of friction nonlinearity suppression to dynamic performance and machining stability.