A　variable　parameter　PI　adjustment　system　based　on　the　fuzzy　control　technique　was　developed,　which　improved　the　performance　of　the　dynamic　response　of　inverter　welding　power　supply　effectively.　DSPIC30F2020　was　used　as　the　core　control　chip,　and　a　two-input　two-output　fuzzy　controller　was　established.　By　taking　the　welding　current　deviation　and　its　changing　rate　as　input　signals,　and　fuzzy　processing　them　respectively,　the　PI　control　parameters　were　optimized,　which　make　sure　the　precise　controlling　of　the　power　output.　With　a　resistive　and　a　capacitive　load,　comparison　tests　between　dynamic　response　of　a　variable　parameter　PI　control　system　and　a　traditional　PI　control　system　were　carried　out.　The　results　proved　that:　The　rise　time　of　a　step　response　of　current　with　variable　parameter　PI　adjustment　is　less　than　0.4ms;　In　short　circuit　transfer　welding,　variable　parameter　PI　adjustment　can　inhibit　the　overshoot　effectively　when　the　load　changes　dramatically,　which　will　be　the　basis　of　the　inhibition　of　welding　spatter.　©　2011　IEEE.