Titanium dioxide (TiO₂)-based materials are commonly used in constructing photoelectrochemical(PEC) sensors due to their advantages, such as an optimal band gap, abundant surface-active sites, and environmental friendliness. These materials hold significant promise for the efficient enrichment and detection of environmental pollutants. However, high recombination rates of photogenerated charges and limited visible light utilization remain challenges that severely restrict the PEC performance of TiO₂-based materials. This paper provides a comprehensive overview of the mechanisms of PEC sensing, key factors affecting PEC sensor performance, as well as various modification strategies such as heterostructure construction, crystal plane adjustment, ion doping, and dye sensitization. Furthermore, the application of TiO₂-based PEC sensors in detecting trace levels of diverse environmental pollutants is discussed. Finally, the paper presents a summary and outlook on the advancements of TiO₂-based materials in environmental detection, serving as a reference for developing highly sensitive TiO₂-based PEC sensors.