The effective utilization of the cryogenic exergy associated with liquefied natural gas (LNG) vaporization is important. In liquefied natural gas during regasification, can be used from available cold energy to recover exergy and production of electric power.LNG is composed of 85–99% methane by mole fraction, a few percent ethane, and propane depending on its production site. Since moisture and sulphur are contained in crude natural gases, they should be removed during the liquefying preprocess. In this project, efficiency of open brayton cycle increases as step by step, that would be made to four cycles. Energy equilibrium equations and exergy equilibrium equations of each component in the any four power cycles are established, and taken some operating parameters as key parameters; influences of these parameters on thermal efficiency and exergy efficiency of the all power cycles were analyzed.The results of four cycles are compared with together and finally a combined cycle is suggested that can recover heat loss of low-temperature, and uses LNG cold energy as well. A novel combined power cycle is proposed which utilizes LNG in different ways to enhance the power generation of a power plant. In addition to the direct expansion in the appropriate expander, LNG is used as a low-temperature heat sink for a middle-pressure gas cycle which uses nitrogen as working fluid. Also, LNG is used to cool the inlet air of an open Brayton gas turbine cycle. This cycle with LNG directly expanding consisting of a middle brayton cycle with nitrogen as working fluid and a power cycle of combustion gas is proposed to recover cryogenic energy of LNG. These measures are accomplished to improve the exergy recovery of LNG. In order to analyze the performance of the system, the influence of several key parameters such as pressure ratio of LNG turbine, the ratio of the mass flow rate of LNG to the mass flow rate of air, pressure ratio of different compressors, LNG pressure and inlet pressure of nitrogen compressor, on the thermal efficiency and exergy efficiency of the offered cycle is investigated. Finally, the proposed combined cycle is optimized on the basis of first and second laws of thermodynamics.The goal of this study is to show how to implement the concept of thermo-economy to this cycle and also how to estimate the entering costs to the final cycle. Cost balances and auxiliary equations are applied to all components in the cycle. At first time, exergyeconomic analysis of the combined final cycle by this form is applied. We get almost 20 million dollars per year from this cycle. Keywords: LNG,thermodynamic analysis, exergoeconomic analysis, Power generation