Fiber-optic Fabry-Perot pressure sensors based on silicon diaphragms of different thicknesses were fabricated using surface and bulk MEMS techniques in this study. The multi-beam interference resulting from multiple reflecting mirrors with the elastic deformation of the Fabry-Perot sensor was simulated by finite element analysis. The pressure sensitivities of the sensors with different diaphragm thicknesses and the relationship between the pressure and the wavelength shift were simulated. The simulation results were in good agreement with the test results. This study provides guidance for future sensor models and parameter design.