Abstract: Glycerol is a major by-product generated during biodiesel production with abundant reserves and low cost. However, its overall utilization efficiency remains low at present, which not only results in the waste of valuable biomass resources but also causes certain environmental burdens. The selective oxidation of glycerol into high-value-added chemicals is recognized as an important pathway to achieve efficient utilization of biomass resources and promote the high-quality development of the green chemical industry. Dihydroxyacetone (DHA), as a core high-value-added product from the selective oxidation of glycerol, is widely used in pharmaceutical, cosmetic and food industries and possesses far higher economic value than raw glycerol. Photoelectrocatalysis (PEC) glycerol oxidation technology integrates the synergistic merits of photocatalysis and electrocatalysis. It enables solar-driven directional conversion of glycerol into DHA under mild conditions of ambient temperature and atmospheric pressure, and thus overcomes the inherent drawbacks of traditional thermal catalysis and electrocatalysis, including harsh reaction conditions, unsatisfactory product selectivity and abundant side reactions. Systematic investigations on the directional conversion of glycerol reveal that the selective activation of secondary hydroxyl groups within glycerol molecules is critical for DHA formation, while C—C bond cleavage acts as the dominant side reaction responsible for decreased DHA selectivity. Three primary reaction pathways exist in the system, namely direct hole oxidation, surface-bound hydroxyl radical oxidation and high-valent metal oxide oxidation. Obvious discrepancies are observed in the influences of these pathways on product selectivity. The research advances and modification progress of typical photoanode materials including TiO₂, BiVO₄ and WO₃ are summarized. The regulating effects of morphology and facet engineering, heterojunction construction, metal doping and loading, as well as surface modification on light absorption capacity, photogenerated carrier separation efficiency and catalytic activity are analyzed emphatically. On this basis, key regulatory strategies to boost DHA selectivity are concluded, including doping, metal loading, defect engineering, heterojunction construction and cocatalyst deposition. The core working mechanism of each strategy is elucidated. Electronic structures can be modulated and DHA desorption facilitated via doping. Metal loading, especially through strong metal-support interaction (SMSI), can create active sites for the selective adsorption of secondary hydroxyl groups. Defect engineering enhances the electrostatic adsorption toward secondary hydroxyl groups by introducing oxygen vacancies or bismuth-rich surfaces. Heterojunction construction can form built-in electric fields to accelerate charge separation and integrate dual pathways of hole oxidation and ·OH-mediated oxidation. Cocatalyst deposition can offer highly selective active centers and reduce reaction overpotential. By comparing the performance parameters of representative photoanodes, the advantages and limitations of each regulatory strategy in terms of glycerol conversion, DHA selectivity, product yield and stability are summarized. It is demonstrated that strengthening the selective adsorption of secondary hydroxyl groups, accelerating DHA desorption and optimizing photogenerated charge transport constitute the core approaches to simultaneously realize high conversion efficiency and favorable selectivity toward the target product.