The invention relates to a fuel cell start-up method, said fuel cell comprising numerous cells which are supplied by a reformer (10). According to the invention, when the reformer is cold, reformates are supplied to a first sub-assembly (12) of cells of the fuel cell and, when the reformer is hot, reformates are supplied to the first and second sub-assemblies of cells of the fuel cell. The cells belonging to the first sub-assembly are optimized in order to operate with a cold reformer and the cells belonging to the second sub-assembly (13) are optimized to operate with a hot reformer.