Utilizing the bulk and surface micromachining technologies, this thesis designed and fabricated a piezoresistive pressure microsensor for developing an in-vivo and real-time biomedical detection microsystem to monitor the uric pressure in patients¡¦ bladder. In this study, the main processing steps include the implantation of a moderate boron ion concentration into the N-epitaxial silicon layer to form the piezoresistors, anisotropic etching the backside silicon substrate to create a cavity by 30% KOH solution in 80¢XC temperature, and anodic bonding of the silicon based pressure microsensor and the hole-drilled glass sustain. To obtain the optimum design specification of the piezoresistive pressure microsensor, this study compared the characterization of the four types of devices with three different pressure sensing area (As) and two different length/width ratios (L/W) of the N-epitaxial piezoresistors. Based on the measurement results, the highest sensitivity (0.0076mV/(V*kgf/cm2) can be achieved as the As and the L/W ratio are equal to 1050 ¡Ñ 1050 £gm2 and 90/9 £gm/£gm, respectively. Such sensitivity is suitable for the application of bladder pressure detection microsystem. A very high sensing linearity (99.6%) can also be demonstrated in this research and this value approach to that of the commercial pressure sensor. On the other hand, through cooperation with another laboratory, this work has established a prototype of the uric pressure detecting microsystem by assembled with the piezoresistive pressure microsensor, a control ASIC and a radio-frequency (RF) module.