Sulfide semiconductor minerals are widely distributed in the earth crust. Some of the sulfide minerals with narrow band gaps, such as pyrite, chalcopyrite, and pyrrhotite, can generate natural thermoelectric potential to convert the thermal energy within the earth to electrical energy under the geothermal gradient. In this paper, the authors selected natural sulfide mineral samples such as pyrite, pyrrhotite, galena, chalcopyrite, bornite and bornite-chalcocite-hematite mineral assemblage to study their thermoelectric properties. The results indicated that, at the temperature of 300~700 K, except that the pyrrhotite exhibited electrical transmission of metal conductors with low Seebeck coefficient and ultra-high conductivity, pyrite and chalcopyrite samples were n-type semiconductors, while bonite and the bornite-chalcocite-hematite mineral assemblage sample were p-type semiconductors, which exhibited significant Seebeck coefficient of 150~500 μV/K and a conductivity of 5~95 S/cm, indicating that samples had the capability for producing significant thermoelectric effects under geothermal gradients. Thermal conductivity was calculated based on thermal diffusivity measured by laser flash diffusivity method, theoretical specific heat capacity and density of the sample, and the results of the thermal conductivity showed that bornite and the sulfide mineral assemblage samples exhibited low thermal conductivity less than 1 W/(m ·K), indicating that the samples could form a large temperature difference under the influence of local heat source. According to the basic theory of thermoelectricity and the geothermal gradient, the authors constructed the natural thermoelectric effect model to calculate the natural thermoelectric potential, additional surface current density and thermoelectric conversion efficiency generated by the sulfide semiconductor minerals, where empirical formulas were summarized. It is found that sulfide minerals can produce a natural thermoelectric potential of about 100 mV at 300~650 K, and the maximum thermoelectric conversion rate can reach 4‰. In addition, the additional surface current density generated by mineral bodies can be calculated by the dipole current source model. Therefore, sulfide semiconductor minerals may act as natural thermoelectric conversion media to profoundly affect the transformation and transfer of energy inside the Earth.