This invention provides a method for synthesis a catalyst for catalyzing hydrogenation of CO2 to methanol. The precipitation process was controlled at 70 oCaging for 1.5 hour. The CuO: ZnO: Al2O3 weight ratios are 7: 3: 1. The particle size of CuO is less than 5 nm. The reaction is carried at 50 bar250 oC, CO2/H2= 1/3. Adding hydrophobic fumed silica, water is expelled from catalyst surface,the reaction can shift to product side. Therefore the CO2 conversion can reach 90 thermodynamic equilibrium conversion, methanol selectivity is greater than 95.