Dimethyl carbonate is directly synthesized by reaction of carbon dioxide and methanol with Ce0.4Zr0.6O2 as catalyst under supercritical conditions. The reaction conditions, such as reaction temperature, reaction pressure and reaction time are optimized through the method of orthogonal test and single factor test. The optimum reaction conditions are as follows: the proportion of Ce0.4Zr0.6O2 and methanol is 1∶50, the reaction temperature is 180 ℃, the reaction pressure is 9.5 MPa and the reaction time is 8 h. Under these optimum conditions, the yield of dimethyl carbonate is 7.48% by GC MS analysis.