Radioisotope thermoelectric generator (RTG) has been widely regarded as a promising battery for space missions. To broaden RTG's application on earth, a terrestrial radioisotope thermoelectric generator (tRTG) was demonstrated in this paper. By employing the finite element analysis, an octagonal cylinder-shaped substituted electric heater and a fin-shaped radiator were manufactured, the heater was designed to have a higher surface temperature and better temperature uniformity meanwhile the fin-shaped radiator could dissipate heat at its optimal heat-sinking capacity. Then, the effects of temperature, electric connection on the output performance of the tRTG were studied experimentally. Lastly, the finite element analysis was carried out to optimize the geometry of thermoelectric converters within a certain area, as a result, the tRTG possessed an enhanced output power of 10.5 W which increased by 26.5%. Throughout this paper, the geometry design and performance optimization of tRTG were presented and discussed. (C) 2020 Elsevier Ltd. All rights reserved.