Magnetorheological　dampers　(MRDs)　are　applied　to　hydraulic　systems,　which　not　only　improve　the　underdamped　characteristics　of　valve-controlled　cylinder　systems,　but　also　help　hydraulic　actuators　to　resist　high　load　impact.　However,　the　high　power　density　leads　to　the　complexity　of　the　internal　flow　channel　of　the　damper,　which　seriously　affects　the　output　accuracy　of　the　damping　force.　It　can　lead　to　the　fact　that　existing　dynamics　models　cannot　accurately　describe　the　hysteresis　characteristics　of　the　MRD.　Therefore,　this　study　proposes　a　simple　and　general　dynamic　model　of　MRD,　which　solves　the　problem　that　existing　models　are　complex　and　difficult　to　invert.　Firstly,　the　hydraulic　damping　actuator　with　the　series　MRD　is　taken　as　the　research　object.　Based　on　the　stress-strain　hysteresis　characteristics　under　the　cyclic　constitutive　model,　the　hyperbolic　tangent　curve　is　reorganized　and　normalized.　It　can　accurately　describe　the　yield　formation　and　yield　dissipation　stages　of　the　hysteresis　loop.　Secondly,　the　relationship　between　the　parameters　of　the　dynamic　model　and　the　current　is　obtained　according　to　the　mechanical　experimental　data.　Then　the　inverse　model　of　the　MRD　is　established　by　using　the　method　of　section-backstepping.　Finally,　in　the　static　experiment,　the　mean　absolute　percentage　error　(MAPE)　of　the　force　at　different　velocity　is　less　than　7.5%;　in　the　dynamic　experimental　test,　the　MAPE　of　the　force　is　9.7%.　The　inverse　dynamics　model　is　verified　to　have　high　tracking　performance　under　both　static　and　dynamic　forces.　And　it　also　indirectly　confirms　the　effectiveness　of　the　forward　model.