In order to simulate the characteristics of thin film bulk acoustic resonator (FBAR) more accurately, a method to modify the FBAR Mason model is presented in this paper. Firstly, the finite element simulation method is used to simulate FBAR, including the mechanical loss and dielectric loss of piezoelectric layer. The obtained admittance curve data is imported into the electromagnetic (EM) model of FBAR by using the equivalent permittivity method, and then the ohmic loss and conductor loss of FBAR electrode can be simulated to obtain the impedance curve of FBAR. The parameters of MBVD model are extracted by fitting impedance curve. The Mason model of FBAR is modified by using MBVD model parameters for reference. Compared with the fitting results, it is found that the series resonance point of FBAR EM model is shifted to the left. It is presumed that the parasitic parameters are introduced into the EM model. Therefore, the parasitic inductance parameters are added to the modified Mason model. At this time, the impedance characteristic curve obtained by the simulation is in good agreement with the simulation result curve of the EM model. The presumption has been verified and a more accurate FBAR Mason model has been obtained.