Active magnetic regenerator (AMR) is the central component in magnetocaloric system, such as magnetic refrigeration, magnetic heat pumping and magnetic energy conversion machines. This paper presents a numerical study on the design of an active magnetic regenerator and its impact on performance in refrigeration mode. Although, plenty of experimental and simulation data are available in the literature for different types of embodiment, it is difficult to make a direct comparison because those studies have been performed under varying assumptions, conditions and geometries. A generic model is used to simulate performances during the operation of an AMR in a refrigeration mode. This model has been set-up for to six different embodiments, and systematic simulations are carried out. The pressure drop, refrigeration capacity, and coefficient of performance are evaluated numerically. A comparison of the performances for each alternative allows us to select the most efficient embodiment. The configuration using flat-parallel plates exhibited the best performances.