To satisfy the performance and reliability requirement of a MEMS based harsh environment sensor, the sensor development needs to depart from the classic method of single-discipline technology improvement. In this paper, the authors will describe a Microsystem-based design methodology which considers simultaneous multiple technology domain interaction and achieves performance optimization at the system level to address the harsh environment sensing challenge. This is demonstrated through specific examples of investigating a robust MEMS gyroscope suitable for high temperature and high vibration environments such as down-hole drilling for Oil and Gas applications. In particular, the different mechanisms of temperature-induced errors in MEMS gyroscope are discussed. The error sources include both the direct impact of the gyroscope dynamics by temperature and the indirect perturbation by temperature-induced package stress. For vibration and shock induced failure, the error contributions from the low frequency and high frequency contents are discussed. Different transducer designs with equivalent rate sensitivity can vary with several orders of magnitude in terms of the susceptibility to mechanical vibration. Also shown are the complex interactions among the gyroscopic transducer, packaging and the control electronics, resulting from these temperature and vibration error sources. The microsystem-based design methodology is able to capture such complex interactions and improve the gyroscope temperature and vibration performance. In contrast to other efforts in harsh environment sensing which focus on specific technology domains, the authors strive to demonstrate the need and advantage of addressing MEMS performance and reliability in harsh environment from a microsystem perspective.