Thermoelectric Generator is a device using the widespread natural temperature to generate electricity. On the basis of investigations and experiments, this paper fully expounded thermoelectric generator’s significance, system block diagram, circuits, operational principle, application foregrounds and etc. Semiconductor thermoelectric module and the controller compose the thermoelectric generator, semiconductor thermoelectric power modules change heat energy into electric energy, the electric energy is stored in the controller's battery by the charging circuit. The controller has many functions such as current limiting, under voltage and other functions. At the same time, we had also designed the step-up circuit, in this way, the thermoelectric generator can output higher voltage. The experiment results and application show the thermoelectric generator has good performance and powerful function, it is worth spreading.