The study uses simulation and experiment to investigate the power capacity of thermoelectric generator modules. The result shows that the power capacity increases with reducing the leg height. Compare with the results of simulation and packaging test, they have the same trend. However, the ratio of power capacity increases with leg height reduce in packaging test is smaller than them in simulation. In the packaging test, the main reason is that the heat loss between the top and bottom substrate is more serious in the shorter the legs. In addition, the shorter legs have the lower temperature difference that influence by the substrate at the same temperature difference between two ends of the module.