The dimethacrylate macromonomer named bis (2-hydroxy-3-(méthacryloyloxy) propyl) fumarate (HMPF) was synthesized by ring opening reaction of epoxide function of glycidyl methacrylate (GMA) with maleic anhydride (MA) in presence of Maghnite-H+ as a catalyst at room temperature and at free solvent. The Maghnite-H+ is a proton exchanged montmorillonite clay it is an Algerian clay activated by sulfuric acid 0,23M. The HMPF was characterized by FT-IR, 1H NMR and 13C NMR spectroscopic techniques. A kinetic study was carried out to determine the amount of the catalyst (5, 10, 20 and 30%) which will give abetter yield of the synthesis reaction. T he yield of the reaction was 62. 2 3% for a quantity of Maghnite-H+ (20% relative to the monomer and for a r eaction time of 72 h.