Aiming　at　the　difficulty　of　precise　location　and　isolation　of　power　quality　disturbance　in　distribution　system,　a　power　quality　monitoring　and　load　protection　system　based　on　intelligent　switch　was　designed.　The　electric　energy　information　is　collected　and　analyzed　on　the　spot　by　the　intelligent　switch.　Load　protection　is　executed　according　to　the　analysis　results.　In　the　process　of　power　quality　analysis,　windowed　Fourier　transform　is　used　to　detect　harmonics.　The　average　current　is　used　to　calculate　the　unbalanced　degree　of　three-phase　current.　The　transient　power　disturbance　is　identified　by　Hilbert-Huang　transform　(HHT).　The　accuracy　of　the　above　algorithm　for　each　indicator　monitoring　is　verified　by　the　co-simulation　system.　Simulate　the　case　where　the　index　is　out　of　limit,　and　the　protective　effect　of　the　switch　on　the　load　is　proved.　©　2021　IEEE.