It will provide powerful support for identifying the operating status of HVDC bushing by on-line measuring the weak current. A novel weak current measuring method based on giant magneto-resistance (GMR) sensor is presented in this paper. The principle of GMR and the GMR based weak current measuring principle are introduced at first, and then the selected GMR sensor is utilized to construct the measuring system. After that, the lab test is carried out. The existing problem and the improving direction are discussed at last.