To disclose processing marks of prehistoric jade and to understand the origin and evolution of ancient mechanical processing methods, a single perforated turquoise bead, unearthed in Peng Nation tomb from the Western Zhou Dynasty, was selected for microwear analysis using a VHX-500K digital microscope with 3D image reconstruction and an extended depth of field. It was discovered that there were clear grind marks on the surface and several parallel round lines on the perforation wall. Through simulated grinding experiment on modern turquoise, and from previous work, it was concluded that the grinding tool should be a kind of grinding machine with coarse and finishing grinding functions. The abrasive used was quite coarse, of larger particle size than that used with modern finishing grinders. As for the perforation, it was perforated from both sides, and could have been made using a high-speed core drill with grinding sand. This was the first application of a digital microscope with extended depth of field in to microwear analysis in China. The results provide useful information for scientific identification of ancient jades and ancient jade processing technique.