The slot milling experiment of AL1060 part was operated by carbide alloy tool with 0.6 mm diameter, the influence of the spindle speed, milling depth, feed rate on the micro-milling force and surface quality in different grain size of AL1060 was analyzed by adopting the method of single factor experiment. The result shows that the micro-milling force is bigger and the surface quality is better of fine-grain AL1060 part than coarse grain AL1060 part, the quantitative test data are obtained, the change trend chart is drew, and the influence mechanism are revealed, research theory and experimental reference are provided for the micro processing performance of different grain size material.