MSs　(Magnetic　switches)　have　been　widely　used　in　situations　where　frequent　on-off　load　are　required.　The　operating　voltage　range　of　the　conventional　magnetic　switch　is　usually　between　85%　and　110%　of　the　rated　control　voltage.　When　the　control　voltage　sags,　the　narrow　operating　voltage　range　might　lead　the　conventional　MS　to　malfunction　causing　an　unintended　operation　of　load.　To　address　this　problem,　a　control　module　is　designed　in　this　paper:　the　control　parameters　of　the　module　are　obtained　from　simulation　result　of　MS　by　Maxwell,　a　bi-coefficient　feedback　control　strategy　is　established　to　improve　the　accuracy　of　coil　current　control,　and　a　waveform　detection　strategy　is　used　to　shorten　the　time　from　the　opening　operation　occurred　to　the　MS　switching　off　the　load　for　increasing　the　operation　frequency.