The invention discloses a method for increasing the photoremediation efficiency of plants by utilizing the joint action of plant growth-promoting rhizobacteria and CO2, belonging to the technical field of bioremediation for radionuclide polluted environments, in particular to a method for increasing the photoremediation radionuclide cesium of plants by utilizing the joint action of plant growth-promoting rhizobacteria and carbon dioxide fertilization. The method comprises the steps of: when phytolacca americana and grain amaranth are utilized to remediate radionuclide cesium polluted soil, carrying out carbon dioxide manure and simultaneously vaccinating the plant growth-promoting rhizobacteria which can resist high-concentration cesium to promote the growth of the phytolacca americana and the grain amaranth by utilizing carbon dioxide induction and microorganism joint action, remarkably improve the overground biomass liveweight of the phytolacca americana and the grain amaranth used for remediating soil and also increasing the absorptive amount of overground cesium of the phytolacca americana and the grain amaranth so as to accelerate photoremediation of the radionuclide cesium polluted soil, increase the photoremediation efficiency, and finally achieve the long-term target of recovering the productivity of land and promoting harmonious and ecological balance and sustainable development of district landscape.