Phenol-contaminated water pollution has become one of serious environmental concerns and remains an urgent problem to be solved for a better quality of life. Phenol belongs to the most toxic compounds. Even at very low concentration, it can be a very pernicious to human beings. Therefore, there has been increasing interest to develop the advanced analysis approach for the detection of phenol in water. Herein, a photoelectrochemical (PEC) detecting platform of phenol has been designed based on metallic Bi self-doping BiOI (Bi/BiOI) materials. This material has been synthesized by a simple one-step solvothermal synthesis with the existence of mild ionic liquid [Bmim]I (l-butyl-3-methylirnidazolium iodide). Glucose plays an important role in reducing Bi3+ to metallic Bi. A series of characterization methods have confirmed that metallic Bi is uniformly distributed over the BiOI. The Bi/BiOI composites based electrodes exhibit superior photocurrent generation due to excellent electron transport of Bi nanoparticles and efficient separation of photoexcited electrons and holes. Moreover, the photoelectrochemical sensor based on Bi/BiOI composites has been designed for monitoring phenol. The Bi/BiOI PEC sensor displays excellent stability, a wide linear region, and low limits of phenol. That is to say, Bi/BiOI PEC sensor platform can be used as an analysis method for the determination of phenol, and simultaneously contributes to broadening the application of BiOI-based materials in the photoelectrochemical field.