The　breaking　and　closing　coils　of　bistable　permanent　magnet　circuit　breaker　(PMCB)　shares　magnetic　circuit,　which　leads　to　the　fast　time-varying　nonlinear　coupling　relationship　between　the　permanent　magnetic　field　and　the　electromagnetic　field,　and　between　the　breaking　and　closing　magnetic　circuits,　which　brings　difficulty　to　its　simulation.　Aiming　at　the　difficulty,　this　article　designs　a　new　cosimulation　method:　First,　the　equivalent　magnetic　circuit　of　the　bistable　permanent　magnet　actuator　(PMA)　is　established,　and　the　ternary　correspondence　relationship　of　its　electromechanical　parameters　is　proved　analytically　for　the　first　time.　Then,　the　＇equivalent　electric　circuit＇　of　magnetic　circuit　in　dynamic　process　of　bistable　PMA　is　proposed　for　the　first　time　by　analogy　with　the　transformer　model,　and　the　calculation　method　of　the　time-varying　parameters　in　this　model　is　given.　Finally,　the　＇equivalent　electric　circuit＇　of　magnetic　circuit　is　used　as　a　link,　so　the　hardware　circuit,　software　strategy,　and　PMCB　are　connected　together　to　form　a　point-by-point　closed-loop　cosimulation　method.　This　simulation　method　can　reflect　the　dynamic　interaction　between　the　electromagnetic　field　and　the　permanent　magnetic　field　of　the　breaking　and　closing　magnetic　circuits,　and　also　can　reflect　the　dynamic　interaction　between　the　control　module　and　the　PMCB.　So　this　method　lays　the　foundation　for　simulation　design　of　the　high-performance　bistable　PMCB.　©　2023　IEEE.