The DC-DC 100A single phase solid state relay is used in the automatic control filed like signal light, scintillator, stage lighting control system, instrument and apparatus, medical equipment, copier, automatic washing machine, automatic fire equipment and security system, and it also can be used as the selector switch of the power capacitor which be compensated by the network power factor. In addition, the DC-DC 100A single phase solid state relay is widely used in the bad environment and frequent switching occasions like the chemical industry and coal industry which need prevent from explosion, damp, dust and erosion.