Hypercrosslinked polymers (HCPs) are a type of porous organic materials with high surface area and maneuverable preparation process. Metal-functionalization is a popular and effective post-synthesis modification strategy to construct catalytically active HCPs. Tannic acid (TA) is a biomolecule containing polyphenol moieties that possess the ability to conduct Friedel–Crafts alkylation reaction and metal-bonding active sites. We utilized TA to prepare the hypercrosslinked polymer (TA-HCP) with 1,2-dichloroethane as the crosslinker. After post-synthesis reaction, the vanadium-functionalized TA-HCP-VO was obtained with well-maintained chemical structure and moderate surface area. TA-HCP-VO exhibits an excellent catalytic performance in thioether oxidation reaction to produce sulfoxide compounds. Various thioether substrates with different substituents are transformed to sulfoxide products with high conversion rates (99%) and selectivities (86–95%) under the catalysis of TA-HCP-VO. Furthermore, heterogeneous TA-HCP-VO retains fine catalytic activity and chemical structure after four cyclic reactions, which demonstrates the superiority of heterogeneous porous catalysts.