In order to solve the pressure measurement problem in harsh environments, such as high temperature above 200 ℃, a special piezoresistive pressure sensor with the ranges of 0～120 kPa is developed based on the Micro Electro-mechanical System(MEMS) and Separation by Implantation of Oxygen(SIMOX) technology. The piezoresistive pressure sensor chip consists of a silicon substrate, a thin silicon dioxide layer, an optimized boron ion implantation layer photolithographically patterned on a Wheatstone bridge configuration, a stress matching layer with silicon nitride, a Ti-Pt-Au beam lead layer for bonding gold wires, and a cavity fabricated by the wet etching. A special buried silicon dioxide layer with a thickness of 367 nm is fabricated by the SIMOX technology with the oxygen ion dose of 1.4×10¹⁸/cm² and an implantation energy of 200 keV. The buried SiO₂ layer is used to isolate the upper measuring circuit layer from the silicon substrate to avoid the leak-current influence, so the fabricated sensor chip can be used in a high temperature above 200 ℃. In order to improve the stability in the wide temperature range, the temperature compensation methods are studied and carried out, so the Temperature Coefficient of Sensitivity(TCS) and Temperature Coefficient of Offset(TCO) of the compensated sensor are easily obtained to be less than 1×10^-4/℃·FS. The calibration results show that the developed high temperature pressure sensor has good performances under 200 ℃ for a linearity error of 0.12%FS, a repeatability error of 0.1%FS, a hysteresis error of 0.12%FS, and the sensor′s accuracy of 0.197%FS. which shows it is able to meet the requirements of modern industry, such as oilcans, wind tunnels, mobiles, petrochemical industry, etc..