A compact thermoelectric energy harvester is developed to harvest the thermal energy from the hot surface of the gas turbine, providing continuous and reliable power for the sensing and monitoring system in the gas turbine. An experimental prototype is built and the performances of the energy harvester with different electrical load resistances and source temperatures are characterized. A mathematical iterative method, taking account of Thompson Effect, line spacing gap heat leakage, material property variations, and thermal resistance of the ceramic covering layer, is used to analyze the performance of the segmented thermoelectric generator (TEG) module with good accuracy. Based on this model, the temperature profiles and heat fluxes along the thermoelements, efficiency, and heat leakage through the filling gap material are analyzed. The prototype, with a source temperature of 325 degrees C, has a voltage output of 2.4 V and power output of 0.92 W, which is more than enough to power a sensor node in the gas turbine. A higher power output can be expected with some improvement on the prototype design.