Micromilling technology is becoming more and more essential in many fields in which the miniature parts are widely applied. Research of tool wear occupies an important part in micromilling studies. The micro end mills of 1 mm in diameter with coating TiAlN were used to conduct micromilling parameters studies on tool wear of side cutting edge for brass H59.With the increase of milling length, the wear amount of side edge increases. When the cutting length is 200 m, the wear band width of tests changes from fast to slow, and the critical point of change occurs. The wear form and wear mechanism of tools were analyzed. The wear forms included coating peeling, the rounding of corner radius and cutting edge chipping, and the wear mechanisms included abrasive wear and adhesive wear. Orthogonal experiments were carried out to obtain significance order of key parameters for the wear band width of side cutting edge and the optimal parameters combination. The orthogonal experiments results show that the significance order of key parameters for wear band width from large to small is feed engagement fz, axial cut depth ap, spindle speed n and radial cut depth ae. The optimal parameters combination obtained is fz=2 μm/tooth, ap=03 mm, n=60 000 r/min, ae=015 mm.