The rapid recombination of carriers and large activation energy of CO2 compromise the efficiency of CO2 photoreduction. Herein, SrTiO3 (STO) with different molar ratios of La3+ and Al3+ double-site homo-crystalline substitution is prepared by a ball-milling molten salt method. The concentration of Ti3+ and excess oxygen vacancies decrease to improve the catalytic activity. Meanwhile, the double sites act as electron transfer platforms for easy electron transfer from the bulk phase to the surface to foster CO2 photoreduction. Not only that, the energy transfer due to doping-induced lattice distortion can potentially enhance the photocatalytic activity. A piezoelectrically polarized electric field is introduced to further expedite charge transport. As a result, the activity of La, Al-STO piezo-photocatalytic CO2 reduction is improved to 39.17 mu mol g- 1 h- 1, which is more than seven times better than that of the pure STO. Furthermore, CO2 adsorbs spontaneously on the catalysts because the thermodynamic energy barrier decreases due to the piezoelectric force, which is verified by densityfunctional theory calculation. This study reveals the great potential of double-site homo-crystalline substitution of STO pertaining to the charge transport kinetics and thermodynamics of the catalytic reaction in the piezophotocatalytic CO2 process.