Abstract: The performance optimization of an irreversible Braytion refrigeration cycle is carried out by taking the cooling load density as the optimization objective using finite-time thermodynamic method.The analytical relationship about cooling load,cooling load density and coefficient of performance are derived.The effects of pressure ratio,the allocation of heat exchanger inventory and heat capacity rate matching between the working fluid and heat reservoirs on the cooling load density of refrigerator are shown by the detailed numerical examples.