Abstract: Spherical tank was one of the most widely used pressure vessels for storing gas and liquefied gas, and was extensively used in petroleum, petrochemical industry, metallurgical industry and city gas supply field. For the surface defect inspection during the tank manufacture, installation and in-service period, magnetic particle testing was an important inspection method. Introduced the actual defect distribution of the spherical tank, for actual defects located at different parts, the corresponding inspection methods were introduced. Magnetic particle testing steps and elements were described in detail, and testing traces of the magnetic particle characteristics, as well as defects in the post-processing methods were introduced. It was helpful for the magnetic particle testing of spherical tank.