The　arc　extinguishing　system　is　the　main　component　of　the　micro　circuit　breaker,　and　the　structural　parameters　such　as　the　arc　extinguishing　grid,　the　size　of　the　outlet　hole,　and　the　contact　angle　affect　the　breaking　capacity　of　the　micro　circuit　breaker.　In　this　paper,　an　arc　simulation　model　is　built　based　on　magnetohydrodynamics.　On　this　basis,　the　transient　process　of　short-circuit　current　is　taken　into　account　to　improve　the　accuracy　of　the　simulation　model,　and　the　validity　of　the　model　is　verified　by　experiments.　Based　on　the　simulation　model,　the　influence　of　arc　extinguishing　grid　and　outlet　hole　size　on　the　arc　extinguishing　ability　of　micro　circuit　breaker　is　analyzed　by　arc　shape　and　external　characteristics.　The　results　show　that　increasing　the　arc　extinguishing　grid　will　make　it　difficult　for　the　arc　to　enter　the　grid,　but　at　the　same　time,　it　can　increase　the　arc　voltage　and　promote　the　extinction　of　the　arc.　In　terms　of　the　outlet　hole,　the　uneven　distribution　of　the　arc　when　the　outlet　hole　size　is　2 mm　and　4 mm　will　cause　the　arc　to　blow　out　from　the　grid,　and　the　phenomenon　of　the　arc　blowing　out　from　the　grid　can　be　effectively　avoided　when　the　outlet　hole　size　is　3 mm.　©　Beijing　Paike　Culture　Commu.　Co.,　Ltd.　2024.