Abstract: Under the global "dual carbon", biomass, as the most abundant renewable carbon resource in nature, has a sustainable large-scale supply capacity and advantages such as carbon neutrality, wide sources and strong economic adaptability. It is regarded as an ideal alternative to fossil resources and an important cornerstone of a sustainable energy and chemical industry system. However, due to the influence of its multi-component interweaving, three-dimensional cross-linked structure and the characteristics of various types of chemical bonds, the efficient utilization of biomass still faces challenges such as complex conversion paths, insufficient reaction selectivity and high energy consumption. Although traditional thermal catalytic methods can achieve a relatively high conversion rate, they often rely on high temperature and high pressure conditions, making it difficult to precisely control the product distribution, and are prone to causing side reactions such as carbon deposition and coking. For this reason, it is urgent to develop green catalytic strategies that can achieve highly selective and efficient conversion under mild conditions. Photoelectrocatalytic biomass conversion is a process that utilizes photocatalysts to absorb light energy and excite electron-hole pairs. Photogenerated holes can selectively oxidize highly reactive functional groups in biomass molecules on the anode side, while photogenerated electrons participate in reduction reactions on the cathode side. Through the precise regulation of the band structure and interface engineering design, the efficiency of carrier separation and migration can be optimized, the occurrence of side reactions can be suppressed, and the selective breaking of specific chemical bonds in biomass and the precise retention of functional groups can be achieved. Thus, high-value chemicals such as gluconic acid and aromatic compounds can be efficiently synthesized under mild conditions. Based on the composition and structural characteristics of biomass, this paper classifies and reviews the research progress of photoelectrocatalytic conversion of cellulose, lignin and their derivatives. For the comprehensive cellulose part, the transformation pathways, product distribution characteristics and influencing factors of typical platform molecules such as glucose and glycerol in the photoelectrocatalytic system were elaborated with emphasis. For the lignin component, it is classified and summarized from two dimensions: the selective cleavage of C-O bonds and C-C bonds in the structure. It covers the application of different photoelectrocatalytic systems in lignin depolymerization and the synthesis of high-value chemical products, and analyzes the advantages of emerging technologies such as dye sensitization systems and three-chamber photoelectrobiochemical systems in improving conversion efficiency and product selectivity. Based on this, the core principles of photocatalyst design were summarized, and effective strategies for enhancing catalytic activity and stability, such as interface engineering, defect control, and doping modification, were discussed. Finally, this paper summarizes the current challenges faced by photoelectrocatalytic biomass conversion in terms of raw material complexity, reaction selectivity and energy matching, and looks forward to future research directions such as high-value utilization of all components of primary biomass and bipolar synergistic catalysis, providing theoretical support and technical references for the study of the mechanism of biomass photoelectrocatalytic conversion and the screening and optimization of catalysts.