Different nickel precursors, i.e., nickel nitrate, nickel acetate and nickel acetate plus citric acid, were used to prepare supported Ni/gamma-Al2O3 catalysts for naphthalene hydrogenation to decalin. The catalysts thus prepared were reduced without calcination and after calcination, respectively. The physicochemical characterization and activity testing results show that the catalyst prepared with nickel acetate as precursor and reduced without calcination possesses modest reduction character, higher adsorption and desorption abilities of H-2, and exhibits most excellent catalytic performance for the reaction with 99.1% selectivity of decalin at the naphthalene conversion of 100%.