Abstract: For the raw materials and manufacturing process, more than 70% of the defects are surface defects, which are harmful for the safety operation of power plant boiler. According to JB / T 4730-2005 standard, iron magnetic surface detection, it is necessary to detect the surface defect with magnetic particle testing method for ferromagnetic material. The magnetic particle testing method, magnetization current, main detection technology and quality control elements were outlined, and the magnetic particle testing process of power station was recommend.