In this paper, uniform Co−B amorphous alloy nanospheres with an average particle size of 50 nm were synthesized by chemical reduction of cobalt ion with borohydride in aqueous solution containing Bu 4 PBr and KCl. Then, Pd was introduced into this system by galvanic replacement reaction (GRR) between Co and Na 2 PdCl 4 . Pd/ Co−B catalysts with different Pd content could be obtained via adjusting the amount of Na 2 PdCl 4 in reaction mixture. The crystal structure, morphology, and surface electronic state of as-prepared catalysts were characterized by XRD, TEM, XPS, and H 2 -TPD. During the liquid-phase hydrogenation of 2ethyl-2-hexenaldehyde, the as-prepared Pd/Co−B catalysts exhibited extremely active and more selectivity to 2-ethyl-1-hexanol than the monometallic Pd and Co−B amorphous alloy, showing potential application in industry. The enhanced performances could be attributed to the highly dispersed Pd on the surface of Co−B prepared by GRR and the synergetic effect between Pd and Co.