Based　on　the　chaos　fractal　theories,　the　characteristics　and　the　internal　evolution　of　arc　fault　were　analyzed,　and　an　arc　fault　diagnosis　method　was　put　forward.　The　chaos　and　fractal　characteristics　of　arc　were　qualitatively　and　quantitatively　analyzed　by　using　the　reconstruction　phase　space　theory　and　chaotic　and　fractal　feature　parameters,　such　as　box　dimension,　correlation　dimension　and　Lyapunov　index.　Then　the　spatial　domain　eigenvectors　and　the　diagnosis　model　of　arc　fault　were　constructed.　The　chaos　and　fractal　characteristics　of　current　pre-　and　post-arc　fault　were　analyzed　to　verify　validity　for　low-voltage　power　systems　with　air　compressors　and　switching　power　supplies.　Experimental　results　show　that　the　fractal　structures　and　the　characteristic　parameters　of　chaotic　fractal　of　current　are　different　in　the　change　of　running　state　and　load.Different　evolution　trend　between　normal　current　and　arc　current,　and　the　chaos　and　fractal　characteristic　parameters　show　different　rules.　The　accuracy　of　arc　diagnosis　model　based　on　this　feature　is　more　than　90%.　Meanwhile,　the　load　identification　rate　is　more　than　90%　under　normal　operation.　©　2021,　Harbin　University　of　Science　and　Technology　Publication.　All　right　reserved.