The single crystalline lithium niobite(LN) piezoelectric thin film fabricated by crystal-ion-slicing(CIS) technique can be used as the piezoelectric layer in bulk acoustic wave (BAW) devices, which has attracted increasing attention in recent years. The performance of BAW filter is closely related to that of BAW resonator, but the simulation and optimization of the BAW resonator based on LN single crystalline film has not been reported in depth. In the present work, the FEM simulation model of the solid-mounted resonator (SMR) is established by using the single crystalline LN thin film as the core piezoelectric layer material, the thickness of the piezoelectric layer and the Bragg reflector layer are designed, with an emphasis on the two-dimensional model simulation of the step structure of the top electrode of the resonator, which provides a theoretical basis for the preparation of high frequency LN BAW filter.