Aimed at the phenomenon of build-up edge in the micro milling experiment the influence mechanism of cutting parameters, cutting fluid, tool geometry parameters, tool surface roughness and workpiece material hardness on build-up edge was studied by analyzing the cause of its formation. The influence of build-up edge on the workpiece precision, cutting force and cutting vibration was analyzed. The main method to inhibit the formation of build-up edge in the process of micro milling was presented.