Abstarct: With the increase in world population, industrialization and improvement in the standard of living, there has been a continuous increase in the consumption of energy. Thus the main aim became to find a cost–effective form of energy that neither affects global warming nor threatens national energy security, therefore geothermal energy has become a significant plaxyer. Geothermal cooling and heating systems are the Ground Heat Pumps (GHP) that collect heat from cellar and transfer it to the installed unit into the building.The main components of this systems are comperessor, condenser, evaporator, ground loops and expansion valve. Energy and exergy analysis and Thermo-economic modeling and optimization of geothermal refrigeration cycle(geothermal heat pump) for domestic water heating are presented in this research. The modeling and optimization of a Ground Coupled Heat Pump (GCHP) with closed Horizontal Ground Heat Exchanger are done with EES program. Exergy destruction amounts of system components calculated and compared with refrence [41] and low differences observes in the amounts. The main source of inefficiency according to the second rule of Thermodynamic is compressor. After compressor, Expansion valve, Condenser, Evaporator, Pipe line of compressor to condenser, Pipe line of expansion valve to evaporator, Pipe line of evaporator to compressor and Pipe line of condenser to expansion valve are the source of inefficiency,respectively. Also, the sensitivity analysis of change in coefficient of performance (COP) with inlet temperatures of water source in heating modes for several samples of refrigerants from different groups are investigated.The results shows that R507a and R410a have the highest COP between them. In optimization model by EES program, the Total Annual Cost is selected as objective function, and optimum design parameters are calculated for minimizing above defined objective function (sum of initial and operating cost) and results are presented. Then the sensitivity of heating capacity, overall heat transfer coefficient of soil and inlet water temperature of condenser in optimum Total Annual Cost are discussed. Furthermore, variations of the Total Annual Cost for some refrigerants from different groups and also for three climatic region of Iran includes Tehran, Yazd and Rasht are calculated and compared.