Abstract: Two types of DC degaussing methods for beam of steel pipe are described in the paper. When steel pipe with magnetism is welded, the magnetic field produced by residual magnetism around beam and that by welding arc consist of a composite magnetic field, if the Lorentz force of the composite magnetic field is greater than the contractility of the magnetic field, the movement angle of the charged particles of welding arc will deviate from normal angle, which reflects by arc-blow in macroscopic view. If the arc's deflection angle is greater than 45°, serious arc-blow will occur in welding process, or otherwise, the arc-blow will not be obvious. The authors establish solid model referring to pipeline, degaussing coils and external air with ANSYS software, and obtain the distribution curves of degaussed H-field. The simulation results by simplifying and resolving the model show that the distribution of H-field appears in symmetric axis of charged solenoid, and the strength of H-field is the weakest in the center of coil, and that of H-field at infinite far location from the coil is zero; and that of H-field of pipe wall at two ends is the biggest along the radial direction, and is zero at infinite far location, the H-field distribution in the middle area is relatively even. DC degaussing method is optimized by the authors.