This research present a easy way to build light-duty water jet cutter, which is design a simple structure of pressure adjustment device. Using a pump from a high pressure washer which is business maturity removed the safety electrical limit switch, a standard abrasive for water jet cutting and a water jet cutting head. Add a pressure adjustment device made pump and cutting head, which are not match, can work together. The pressure adjustment device is also a safety device. This simple structure of pressure adjustment device is the way to build a light-duty water jet cutter.