Abstract: For columniform surface corrosion defect of tank floor, according to the basic theory of electromagnetic field finite element analysis, magnetic flux leakage filed of columniform surface corrosion defect is analyzed statically, and the magnetic flux leakage filed spatial distribution of columniform surface corrosion defect is found by means of 3D finite element of ANSYS. In given condition the static simulated magnetic flux leakage field is heavily affected by the magnetic field of permanent magnet in magnetizing system, and the distortion of distribution of magnetic flux leakage field near permanent magnet is caused. The dynamic simulated magnetic flux leakage field changed visibly around the defect, which is hardly affected by the magnetic field of permanent magnet in magnetizing system. It is good for the analysis of corrosion defect.