Liquid natural gas is mentioned to a type of gas that is converted to liquid gas for the purpose of storage or transportation at the large volumes. In this work it has been tried to analyze the LNG cycle with the aid of thermodynamical analysis and parametric investigations on the liquefaction of natural gas cycle. With these investigations it was known that some parameters such as isentropic efficiency of compressor, efficiency of heat exchangers, pressure ratio of compressors and methane temperature have a significant influence on the general efficiency of the liquefaction of natural gas cycle. Finally for having the best efficiency of the related cycle, the optimized results of the investigation is provided.