Photoelectrochemical glycerol oxidation coupled with hydrogen generation is emerging as a sustainable approach for chemical production. However, low efficiency, weak selectivity and poor stability limit the application of glycerol oxidation for value-added chemicals. In this work, we developed a spatial ternary WO₃/BiVO₄/Bi cascade heterostructure for selective glycerol oxidation with high conversion rate and dihydroxyacetone (DHA) selectivity. It was revealed that the existing cascade heterostructure forms a cascade built-in electric field and large surface band bending, which facilitate rapid charge transport and efficient light absorption. Moreover, the Bi⁰/Bi³⁺ interface is proved to promote the interaction with the middle hydroxyl of glycerol to optimize the selectivity for DHA. The novel photoanode demonstrated an efficient glycerol conversion rate of 379.9 mmol m⁻² h⁻¹, a DHA selectivity of 60.6%, and excellent stability, and it can be easily amplified to be a uniform large-sized photoanode. This work provides an innovative method of PEC anode heterostructure engineering for obtaining PEC value-added products from biomass and offers a feasible strategy for high-performance optoelectronic devices.