This study aims to improve the performance of the propane precooling cycle used for precooling of both natural gas and mixed refrigerant in the Propane Precooled Mixed Refrigerant cycle (PPMRC) in an LNG plant. The unit is simulated by Aspen HYSYS version 7.3 for optimization of the propane precooling cycle to provide the minimum energy consumption of the propane compressors and the two air coolers. The effect of subcooling temperature in the propane air-cooler, the number of compression stages in :the propane cycle, and the quality of the natural gas:feed are investigated. Results reveal the extent of reduction in power consumption on decreasing the subcooling temperature of liquid propane. The optimal subcooling temperature of liquid propane and number of compression stages in the propane cycle is determined. The positive impact attained in the performance of the propane cycle is higher for lean feed' gas than for rich feed gas. The decrease of liquid propane subcooling temperature has a dominating influence on all performance criteria and, hence, can be considered as the key contributor affecting the propane precooling cycle in the PPMRC liquefaction process.