Polyoxometalates (POMs), as a unique kind of metal-oxygen cluster compounds, can undergo multi-electron transfer while maintaining their structures unchanged. In this work, an electrochemical sensor that can detect vanillic acid rapidly and sensitively was synthesized with vanadium substituted polyoxometalate (PMoV), reduced graphene oxide (rGO) and Pt nanoparticles (PtNPs), while the PMoV acting as both photoreductant and stabilizer. For this purpose, PMoV/rGO/Pt composite was firstly prepared and identified by various methods. Under the optimal conditions, the limit of detection (LOD) of the electrochemical sensor was attained to be 0.9 μM in 50–1350 μM. Also, the practical application of PMoV/rGO/Pt/GCE was considered by determining the concentration of vanillic acid in tap water and lake with good recovery (98.36%–102.11%, and 97.11%–100.22% respectively). The sensor prepared by this method can realize simple, rapid and economical detection of vanillic acid, and can be used as an important analytical tool in this direction.