Refrigeration is the process of removing heat from substance or space to reduce its temperature and transferring that heat to another substance or refrigeration is providing and maintaining the temperature below that of the surrounding temperature.To produce this effect requires certain machinery, hence, the method is called mechanical refrigeration.One of applications of refrigeration is ice plant.10 tons per day of block ice plant is studied for COP improvement.This plant is located in Yangon, Myanmar.Design calculation of compressor, evaporator and COP of existing ice plant are determined. Ammonia is used as refrigerant in this plant. To improve COP of ice plant, refrigerant changing can be considered. If R-22 or R-134a is used, COP improvement occurs. COP with R-22 is 3.88. COP with R-134a is 3.94.