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Thermal stress is one of the main sources of errors of micro-electromechanical systems (MEMS) devices. The Wheatstone bridge is the sensing structure of a typical piezoresistive MEMS pressure sensor. In this chapter, the thermal stress induced by potting adhesive in MEMS pressure sensor was investigated by experiments, calculated by analytics, and analyzed by simulations. An experiment system was used to test the sensor at different air pressures and temperatures. The stress error becomes greater with the decrease of pressure. A set of novel formulas were proposed to calculate the stress-strain on the Wheatstone bridge. The error increases with the temperature deviating from 25℃. A full-scale geometric model was developed, and finite element simulations were performed, to analyze the effect of the stress on MEMS pressure sensor induced by different temperatures and thicknesses of potting adhesive. Simulation results agree well with the experiments, which indicates that there is a 3.48% to 6.50% output error in 0.35 mm potting adhesive at 150℃. With the thickness of potting adhesive increasing, the variations of output error of the Wheatstone bridge present an N-shaped curve. The output error reaches a maximum of 5.30% in the potting adhesive of 0.95 mm and can be reduced to 2.47% , by increasing the potting adhesive to 2.40 mm.