Abstract: To analyze the phenomena of extra transverse magnetic field excited by the magnetic control arc sensor in submerged arc welding seam tracking system,finite element method was adopted.The simulation model of the transverse magnetic field was set up and FSW code ANSYS was utlized to calculate the according model.Distribution of longitudinal section of transverse field in magnetic control arc sensor and magnetic density vector were both analyzed.Then the consistency of simulated value and measured value of magnetic induction density were verified.After that the deviation of simulated result were tested.Finally,the welding arc the state of motion influenced by exciting current were also researched.The results showed that the welding arc swang with the increasing excitation current,the greater excitation current,the greater arc swings greater.