Abstract: The invention relates to a process of reduction of a refining catalyst before its use, the catalyst containing a support and an active phase with a base of at least one noble or nonnoble metal of Group VIII or Group Ib of the periodic table, the process consisting in:a) impregnating the catalyst with an aqueous or organic solution of a reducing agent compound,b) breaking down the reducing agent compound by heating the catalyst;c) drying the catalyst thus obtained.The invention is characterized in that a halogen additive is added with the reducing agent.The catalyst thus treated is particularly suitable, for example, for selective hydrogenation of unsaturated hydrocarbons.