The minimization of mechanical parts is one of important research direction in micro machine or MEMS area. Milling experiments of micro part were conducted on micro machine by using TiAlN-coating micro-diameter cutter. Three kinds of typical workpiece materials (LY12, stainless steel and high-elastic alloy 3J21) were adopted and the wear properties of micro-diameter cutter were investigated carefully. The main reasons for tool wear and breakage were analyzed. It is shown that the common wear characteristics of TiAlN-coating micro-diameter cutter are falling off of coating, breakage of tool nose, diffusion and adhesion wear while machining the three materials. Adhesion and diffusion effects are much obvious in machining 3J21 alloy and stainless steel, leading to coarse wear region of tool.