Large amounts of anthropogenic CO₂ emissions associated with increased fossil fuel consumption have led to global warming and an energy crisis. The photocatalytic reduction of CO₂ into solar fuels such as methane or methanol is believed to be one of the best methods to address these two problems. In addition to light harvesting and charge separation, the adsorption/activation and reduction of CO₂ on the surface of heterogeneous catalysts remain a scientifically critical challenge, which greatly limits the overall photoconversion efficiency and selectivity of CO₂ reduction. This review describes recent advances in the fundamental understanding of CO₂ photoreduction on the surface of heterogeneous catalysts and particularly provides an overview of enhancing the adsorption/activation of CO₂ molecules. The reaction mechanism and pathways of CO₂ reduction as well as their dependent factors are also analyzed and discussed, which is expected to enable an increase in the overall efficiency of CO₂ reduction through minimizing the reaction barriers and controlling the selectivity towards the desired products. The challenges and perspectives of CO₂ photoreduction over heterogeneous catalysts are presented as well.