Abstract: The traditional piezoresistive pressure sensor has high sensitivity but also high nonlinearity. To solve this problem, this paper designs a new piezoresistive pressure sensor with a sensing diaphragm of beam-membrane-three-island structure. By designing three square island structures on the sensing diaphragm, the linearity and overload resistance of the sensor are improved. At the same time, the stress concentration zone is formed by the short narrow beam structure designed on the sensitive diaphragm to ensure the high sensitivity of the pressure sensor. The structure is simulated and analyzed, the mathematical model between the size parameters of the pressure film and the mechanical properties is established, and the parameters of the mathematical model are analyzed, fitted and solved. Finally, the extreme values under the nonlinear constraint conditions are solved to complete the size optimization, so that the performance of the sensor is improved. The optimization results show that the sensitivity of the pressure sensor is improved and the mechanical properties are good under the condition of ensuring the low nonlinearity of the sensor.