The propane mixed refrigerant cycle（C3/MRC）is the most cost-effective and reliable base-load LNG process.In this paper，two kinds of representative raw natural gases No.1 and No.2 are chosen to study this cycle by using Aspen HYSYS process simulation software，taking into account changes in the cyclic pressures and compositions of mixed refrigerant.Through the research，the functions of mixed refrigerant component N2，CH4，C2H6，and C3H8 in the refrigeration for C3/MRC cycle，are obtained.More importantly，the interrelations between mixed refrigerant composition and raw natural gas’s specific heat vs temperature（cp-T）property，as well as the mixed refrigerant cyclic pressures，are also obtained，thus fully demonstrating the refrigeration functions of mixed refrigerant components in the cycle.On the above basis，the energy consumptions of C3/MRC cycle are compared between the natural gases No.1 and No.2 under different cyclic pressures of mixed refrigerant condition.The results show that the cp-T property of raw natural gas is the dominant factor to determine the level of the whole cycle’s energy consumption，while the mixed refrigerant composition and cyclic pressures are secondary factors relatively，which should be selected appropriately in terms of the cp-T of raw natural gas to make the cycle design more reasonable.