The paper describes the fabrication, designing and the performance analysis of a Piezoresistive MEMS pressure sensor. This pressure sensor uses double polysilicon nanowires to increase the sensitivity of the pressure sensor. The pressure sensor uses circular diaphragm which was fabricated using Reactive Ion Etching method. The pressure sensor has a radius of about 500 nm and thickness of about 10 nm. The polysilicon nanowires form a bridge like appearance between the diaphragm and the substrate. Intellisuite software is extensively used to carry out the finite element analysis. Finite element method (FEM) is adopted to optimize the sensor output and to improve the sensitivity of the circular shaped diaphragm polysilicon nano wire Piezoresistive pressure sensor. The optimum position is also analyzed to place the nanowire to get maximum output. The proposed double polysilicon nanowire pressure sensor gave a sensitivity of about 440 mV/VK Pa.