The global increase in carbon emission is one factor in using clean fuels to minimise air pollution by avoiding fossil fuel usage in the marine sector. The current effort of changing the energy source to LNG fossil gas fuel was assumed to be the cleanest fuel due to lower carbon emission to ease the rapid growth of carbon emission. Recent development in the LNG market drives the shipyard industry to build the LNG offshore platform FLNG, which is like the LNG plant with no land base but offshore. The LNG marine industry forecasts that increasing demand for FLNG vessels will accelerate the de-velopment of gas resources, research work on the system process analysis and optimisation of the Liquefaction system. The rapid growth in equipment and processes of FLNG development is the response to weight and space limits challenges. This paper describes the optimisation process of LNG turboexpander technologies’ benefits based on the different pro-cesses. Since the Single Nitrogen Expander that less efficiency and irreversible losses, another consideration of the dual expander process models and comparison from the simple model to the complex expander process. This article will focus on the LNG liquefaction research process results and analyses the design and optimisation based on power consumption, LNG production and future research directions of FLNG. This research is to aid in a small-scale liquefaction process with a refrigerant cycle proposed in this study to meet these FLNG challenges. The research methodology is to study all models of the expander liquefaction process and analyse the differential pressure of natural gas entry to vary the temperature, heat flow, exergy, and enthalpy. The Aspen Plus and Hysys simulator used a state-of-the-art run simulation for processes for all models.