This work deals with the study of the first stage hydrogen magnetic liquefier operating through an active magnetic regenerator (AMR) cycle, over the temperature range: 298-233 K. For this purpose, an unsteady and one-dimensional numerical model has been developed for predicting the thermal performances of such a liquefier. The transient energy equations are considered to account for the heat transfer between magnetic refrigerant and hydrogen flowing throughout the regenerator bed. The gadolinium has been chosen as a constitute material for the regenerator bed. Simulation results including mainly the cooling capacity and the coefficient of performance (COP) of the AMR cycle as functions of the cycle frequency, the mass flow rate, and the applied magnetic field, are presented and discussed. The capability of the numerical model of predicting consistent results has been shown. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.