It　is　a　common　power　supply　method　in　the　power　distribution　system　that　energy　extracted　from　the　bus　current　supplies　power　to　the　intelligent　monitoring　devices.　The　ability　to　extract　energy　is　directly　related　with　the　dimension　of　the　core　and　the　parameters　design　of　the　energy　harvester.　The　present　literatures　only　consider　the　case　where　the　core　works　on　unsaturated　region,　which　rarely　consider　the　case　where　the　core　works　on　saturated　region.　In　this　paper,　the　effects　of　the　core　saturation,　the　voltage　ripple　of　the　load,　voltage　drop　of　the　rectifier　diode,　winding　resistance　and　the　number　of　turns　are　fully　considered,　and　the　output　voltage　theoretical　model　of　energy　harvester　is　established.　The　validity　and　accuracy　of　the　output　voltage　theoretical　model　analysis　is　verified　by　experiment　and　simulation.　To　maximize　the　output　characteristics　of　the　energy　harvester,　the　capacitance　compensation　circuit　is　proposed.　When　the　core　is　not　saturated,　the　capacitor　plays　a　role　of　resonance.　When　the　core　is　saturated,　the　capacitor　provides　some　negative　volt-second　product　to　lift　the　output　voltage.　The　output　voltage　theoretical　model　provides　a　more　complete　and　effective　approach　for　the　optimal　design　of　the　energy　harvesting　current　transformer　parameters.