Abstract: A finite element method based on ANSYS is proposed to analyze love wave sensors. Firstly, with one dimensional approximation hypothesis and periodic boundary condition, a three dimensional finite element model of love wave sensor is developed, which is composed of substrate, electrode and guiding layer. The eigen frequencies can be extracted by the FEM anlysis. Then, the electromechanical coupling factor is calculated by the eigen frequencies of open and short circuit conditions while mass sensitivity is calculated based on perturbation theory. In the end, the optimum layer thickness is determined by the two parameters. With the variation of guiding layer thickness, the results of both SiO₂/ST-90°X cut quartz and SiO₂/36°Y-X LiTaO₃ devices are presented. The optimum layer thickness is about 0.11 A and 0.2 A respectively. The simulation results are compared with the reported experimental result. It is obvious that the approach in this paper is better than conventional multi-layered method which omitted the electrodes' effect. The proposed approach is expected to provide effective guidance for love wave sensors design.