Polymer Electrolyte Fuel Cells (PEMFC) are the most promising energy source candidate due to their excellent properties such as ease of their operation and maintenance, having high energy density, having higher efficiency than the internal combustion engines and their non-toxic emission. Proton exchange membrane is regarded as the heart of the PEMFC. Today, perfluoro sulfonic acid membranes are the most widely used membranes. However proton conductivity of these membranes is very small at high temperatures and they are very expensive. Therefore studies have been focused on the investigation of alternative membranes. In this study, it is aimed to synthesize an organic-inorganic composite membrane that has better properties than the Nafion(R) membrane. The synthesis of sulfonated polystyrene/polyvinyl alcohol composite membranes with different additives namely, boron phosphate or boric acid were carried out. Also these membranes were subjected to the characterization experiments such as, determination of water uptake capacity and ion exchange capacity, thickness measurements, Scanning electron microscope (SEM), FT-IR, Thermorgravimetric analysis and electrochemical impedance analysis (EIS). As a result of all these studies it was determined that the membrane coded as SPS-PVA-9PB has the highest proton conductivity (0.047 mS/cm), ion exchange capacity (1.46 meq/g) and water uptake (%20.78). Regarding the values reported in the literature and depending on the knowledge gained during the fuel cell studies it was concluded that any membrane which has the above properties is suitable for the fuel cell applications.