A photoelectrochemical (PEC) biosensor based on SnO2 nanoparticles (SnO2 NPs) was developed and applied for phosphatidylcholine (PC) detection in soybean oil. SnO2 NPs were grown on an indium tin oxide (ITO) electrode, polythionine (PTh) was electropolymerized on the surface of ITO/SnO2 NPs, and choline oxidase (ChOx) was immobilized to prepare the ITO/SnO2 NPs/PTh/ChOx electrode. The developed PEC biosensor can detect PC under visible light irradiation. The experimental conditions for PC detection were as follows: 1.8 mg mL-1 ChOx concentration, 0.5 V bias voltage, 18 mW cm-2 light intensity, and pH 6. The PEC biosensor had a detection limit of 0.005 mM (S/N = 3) and a detection range from 0.03 mM to 4 mM. This PEC biosensor based on SnO2 NPs was applied to detect PC in soybean oil. The recovery rate tested by the standard addition method was 95.2-107.4%. These findings were consistent with the results obtained by high-performance liquid chromatography (HPLC). Therefore, the proposed PEC biosensor based on SnO2 NPs has excellent reproducibility, stability, and great potential applications in the PEC analysis of PC in soybean oil.