In this paper, a thermoelectric generator (TEG) with a new compact structure was developed. The TEG composed of two heat transfer exchangers for heating and twelve heat transfer exchangers for cooling, and twenty thermoelectric modules between them. An experiment evaluating the performance of the TEG was carried out. As the result, 34W of electric power was realized at 2.4A current for two thermoelectric modules in series and totally 359W of electric power was obtained in this TEG with a compact volume of only 3 liter. That means the density of generating electric power is more than 100W/L. It is a remarkable improvement comparing with usual TEG less than 40w/L up to now.