The invention discloses a high-efficiency liquid phase aldehyde hydrogenation cobalt metal catalyst and a preparation method thereof. The method is suitable for preparing a cobalt system liquid phase hydrogenation catalyst through an impregnation technology. The method comprises the following steps: adding an active carbon carrier to an aqueous cobalt salt solution A, stirring the carrier and the solution, carrying out water bath treatment, drying the treated mixture to obtain an unformed catalyst, uniformly dropwise adding a potassium borohydride solution to the unformed catalyst, washing the obtained material, drying the washed material to obtain a catalyst precursor, introducing nitrogen and hydrogen to the catalyst precursor, and carrying out roasting activation to obtain the catalyst. The catalyst obtained in the invention has the advantages of very high activity, very high specific surface area, realization of high-efficiency catalysis of liquid phase aldehyde (propionaldehyde, butyraldehyde, isobutyraldehyde and octenal) hydrogenation, and good industrial application prospect.