©　2014　IFSA　Publishing,　S.　L.　A　modeling　approach　for　a　kind　of　the　nonlinear　dynamic　system　is　studied　in　this　paper.　At　first,　suppose　that　the　original　nonlinear　dynamic　system　is　expressed　by　the　nonlinear　Hammerstein　model,　the　transfer　function　of　the　model　can　then　be　changed　into　a　linear　form　by　using　the　function　expansion,　accordingly,　an　intermediate　model　is　generated.　Secondly,　the　parameters　of　the　intermediate　model　are　attained　based　on　a　fish　swarm　optimization　algorithm.　Thirdly,　through　the　parameters　relationships　of　the　intermediate　model　and　the　Hammerstein　model,　we　derive　the　parameters　of　the　Hammerstein　model;　consequently,　the　modeling　of　the　original　nonlinear　dynamic　system　is　achieved.　Finally,　the　feasibility　of　the　presented　modeling　method　for　the　nonlinear　dynamic　system　is　illustrated　by　the　numerical　simulation　experiments.