The present invention provides a catalyst for producing hydrogen and a preparing method thereof. The method includes the steps of adding a first metal source, a second metal source, a third metal source and a cerium source into a first organic solvent containing a surfactant to form a colloidal mixture, wherein a metal of the first metal source is a Group IIIB metal; a metal of the second metal source is selected from the group consisting of alkali metals, alkaline earth metals and Group IIIB metals, and a metal of the third metal source is a transition metal; calcining the colloidal mixture to form a metal solid solution; and allowing the metal solid solution to be carried on a carrier to obtain the catalyst. When the catalyst of the present invention is used for an ethanol oxidation reformation, the reaction temperature of the ethanol oxidation reformation can be significantly decreased. After the catalyst is used for long periods of time, the ethanol oxidation reformation still has high ethanol conversion ratio and hydrogen selection ratio.