The energy exchange between natural semiconductor minerals and chemoautotroph microbes was investigated in details in this paper. Photo_electrochemical experiments indicate that the photoelectrons generated by natural semiconductor minerals in solar light can reduce ferric ion to ferrous ion. The reduction efficiency of natural rutile is 12.5% and that of natural sphalerite is 7.86%. This process, which is driven by the photo_catalysis of natural semiconductor minerals, realizes the energy transformation from solar energy to electric energy and finally to chemical energy as stored in the form of ferrous ion. The potential control experiment shows a linear relationship between the amounts of cell growth (A.f.) and the electrons needed for ferrous reduction. Meanwhile the amount of A.f. with electrons flowing in is 4.41 times greater than that of the control group. This process realizes the energy transform from chemical energy to biomass energy by microbe metabolism. Further experiments, which integrate the two processes by an electrochemical cell, indicate that the logarithm growth period of A.f. is extended from 36 h under the dark condition to 72 h under the light condition. Meanwhile, an obvious improvement of cell growth is observed. The concentration of A.f. under the light condition is 1.90 times higher than that under the dark condition when the mineral is sphalerite, while the number is 1.69 times higher when the mineral is rutile. The results demonstrate that the growth of chemoautotroph microbes can be favored by an indirect utilization of solar energy under the assistance of semiconductor photo_catalysis, thus realizing the energy transformation from solar energy to electric energy, chemical energy and finally to biomass energy.