Arc　welding　inverter　supply　with　switch　and　digital　control　is　widely　used,　due　to　the　advantages　of　high　controllability,　small　size,　and　high　efficiency.　With　the　constant　increasing　of　switching　frequency　and　decreasing　of　arc　welding　machine　size,　the　conducted　electromagnetic　interference　(EMI)　becomes　serious,　especially　for　commonmode　(CM)-conducted　EMI.　Mean-while,　as　the　development　of　digital　processing　technique,　digital　active　EMI　filter　(DAEF)　technology,　which　uses　digital　control　and　embedded　mode,　has　become　a　hot　research　topic.　However,　the　conventional　DAEF　fails　to　consider　time　delay　effect.　Its　model　cannot　accurately　describe　DAEF　filtering　behavior.　Moreover,　decoupling　circuit　lacks　scientific　design　method.　To　cope　with　these,　this　paper　proposes　a　precise　DAEF　model　which　considers　both　the　time　delay　of　digital　processing　portion　and　the　parasitic　parameters　of　passive　components.　Moreover,　based　on　impedance　matching　principle,　a　detailed　and　scientific　design　method　of　decoupling　circuit　is　put　forward.　Meanwhile,　the　arc　welding　inverter　system　with　embedded　DAEF　is　designed,　modeled,　and　compensated.　Finally,　experiment　results　show　that　the　proposed　precise　model　can　predict　the　system　filtering　performance　accurately.　And　the　proposed　design　method　of　decoupling　circuit　is　very　effective　to　suppress　the　CM-conducted　EMI.　The　embedded　DAEF　can　improve　system　stability　and　dynamic　performance.