A type of MEMS double Si3N4 resonant beams pressure sensor is presented in this paper. The maths models are established in allusion to the Si3N4 resonant beams and pressure sensitive diaphragm. Based on the maths model of Si3N4 resonant beams, the relation between the resonant frequency and key dimension of Si3N4 resonant beams is analyzed theoretically by the vibration differential equation, at the same time, the simulation is done by the finite element analysis software ANSYS10.0 and the results show good agreement with the theory. At the last, The microfabrication craftwork is designed.