Proton Exchange Membrane Fuel cell (PEMFC) is one of the types of fuel cells that potentially able to be an alternative energy sourcethat environmentally friendly to overcome the energy crisis of fossil fuels in the future. The objective of research to product and characterize the composite membrane of chitosan-CaO phosphorylated as PEMFC. PEMFC made by chitosan and CaO with concentration variation of 0, 10, 15, 20, 25, and 30% (w/w). First, chitosan-CaOdope solution is made. Then, Crosslinking process of chitosan-CaO composite membrane is submerged in solution of 0.005glutaraldehyde and phosphorylation process is done by soaking the membrane in solution of STPP 2N. Characterization of membrane was encompassed by determination of the mechanical properties by tensile test, ion exchange capacity test, water swelling test, analysis of functional groups by FTIR, analysis of membrane morphology by SEM, methanol permeability test, and proton conductivity test. The addition of CaO 25% (w/w) is the most optimal production of phosphorylation chitosan-CaO composite membrane. The membrane exhibited stress of 32 kN/cm2, Young's modulus of 1.3 kN/cm2, ion exchange capacity of 2.413 meq/g, swelling degree at 26.65%, methanol permeability at 1.61x10-3 kg/m2s, and proton conductivity at 4.75x10-5 S/cm. Based on the analysis results, the phosphorylation chitosan-CaO 25% (w/w) composite membrane has good potentials for the application of the polymer electrolyte membrane in PEMFC.