Based on the research of measuring head sensing technology, wireless data transmission technology and CNC machine tool control signal transmission principle, a set of magnetic subassembly, which utilized the force caused by magnetic induction to reset measuring rod precisely, was designed to achieve repeat positioning accuracy within 1 μm for measuring head. Such measuring head equipped with magnetic subassembly was tested to measure diameter 30 mm standard steel balls on CNC machine tool. After 50 000 times continuously test, the steel ball diameter difference calculated and analyzed by macro program of computer software was controlled less than 1 μm. The Testing results prove that the accuracy meets requirements. 