Complex rotor system usually contain multistage bladed disks, which result in tremendous DOFs when leveraging FEM to analyze its dynamic characteristics. Computation efficiency also remains to be improved since the DOFs of single bladed disk is still large even though leveraging the rotation period characteristics. With the purpose of DOFs reduction,simplified and equivalent modeling of single bladed disk can be treated as a feasible way. In this paper,an equivalent modeling method is proposed to simplify the blade group into an annular plate with variable parameters based on the criterion that dynamic characteristics of annular plate canstay approximately the same as the original one. Physical parameters of annular plate including geometric and material parameters can be obtained by theoretical derivation and calculation. In the end of the paper, the equivalent modeling method is verified by taking a bladed disk model of aero engine as an example. It turns out that the equivalent modeling method can not only ensure precision but also improve computational efficiency.