The invention discloses a preparation method of a catalyst for synthesizing hexanediamine by carrying out hydrogenation on hexane dinitrile. The catalyst is an amorphous state nickel alloy catalyst, and is prepared by the method comprising the steps of (1) preparation of catalyst powder: firstly, preparing ammonia water and nickel nitrate into nickel-ammonium complex solution, mixing the nickel-ammonium complex solution with modifying agent water solution, stirring, carrying out hydrothermal aging, filtering separation and drying calcination on the mixture, filling hydrogen, and reducing at high temperature to obtain the catalyst powder; (2) activation of the catalyst: slowly feeding the catalyst powder into NaOH solution, heating and stirring for a certain period of time under the condition of microwave; after the reaction is completed, removing the upper-layer alkali liquor, washing the product to be neutral with deionized water, and washing with absolute ethyl alcohol for later use. The activity of the obtained amorphous state nickel alloy catalyst is evaluated by the conventional reaction conditions. The catalyst is uniform in distribution of active components, and the conversion rate of the hexane dinitrile and the selectivity of the hexanediamine are higher.