Abstract: IGBT arc welding power source will generate serious EMI. Experientially, filtering, shielding and grounding are three important ways to reduce EMI. Compare tests were taken to analysis the suppression methods according to CISPR 11, which specified provisions for the test site measurements and limits of electromagnetic disturbances. And compare conducted emission and radiated emission for both the soft-switching welder and hard-switched welder under same working conditions. It found that choosing appropriate topological structure and component parameter of filter can effectively suppress the conducted emission. And the EMI suppression effect is not ideal when using soft-switching technology.