Magnetocaloric systems are interesting from the point of view of energy efficiency and could be environment-friendly products. Numerous prototypes have demonstrated the feasibility of such systems for applications around room temperature, but there is still room for improvement. The research of an optimal configuration only by an experimental approach is a complex and difficult task due to numerous building parameters and driving parameters. Therefore we propose here a methodology based on a numerical approach. A numerical model calibrated with respect to experimental tests is used to make a parametric analysis of a magnetocaloric system. The design of the system is made according to given functional specifications, targeting different design strategies such as the power density, the energy efficiency, the maximizing of the temperature span, etc. This work is a step forward to the increase of the efficiency in the design of our future systems