A novel cation exchange membrane consisting of polyvinylidene difluoride (PVDF) was prepared for the application of vanadium redox flow battery (VRFB). PVDF used as supporter has considerably high mechanical strength and an intrinsic hydrophobicity. For the successful preparation of the membrane, PVDF powders were modified by potassium hydroxide, which increased the hydrophilicity of PVDF powders. Modified PVDF were grafted with styrene sulfonic acid (SSA) using benzoyl peroxide (BPO) as initiative. The cross-sectional morphology and structure of PVDF/SSA was confirmed by scanning electron microscopy (SEM) and FT-IR. The membrane was characterized by water uptake, dimensional change, ion conductivity and ion exchange capacity (IEC) and cell performance of Vanadium Redox Flow Battery (VRFB) with Nafion 212.