Dry milling the hardened steel is the new way of high efficiency and high quality processing of die and mould. In this paper milling hardened steel has been carried out using coated cemented carbide micro-end mill (Phi2mm) at a mid-high speed. The surface roughness, machining vibration and chip top are analyzed in different cutting parameters (cutting speed, feed per tooth, axial cutting depth). It's clear that the influential rules of the cutting parameters on the surface quality and the unique surface forming rules are understood. The research results show that surface roughness required by finishing can be achieved with rational cutting parameters (R-a<0.4 mum).