This research has explored the effect of adding potassium to nickel supported on gamma -alumina in the selective hydrogenation of 1,3-butadiene. The catalysts containing 15 wt% Ni and varying amounts of K ((K/Ni+K)(atomic) = 0.2-0.6) were prepared by impregnation and characterized by temperature-programmed reduction (TPR), chemisorption of H-2, X-ray photoelectron spectroscopy (XPS) and X-ray absorbance near edge structure (XANES) spectroscopy. Activity and product selectivities were tested for hydrogenation of 1,3-butadiene in the temperature range of 373-673 K. The catalytic activity for the hydrogenation of 1,3-butadiene is closely related to the specific surface area of nickel metal and the crystal structure of the oxide, from which the metal was formed by reduction. The addition of potassium increased the 1-butene selectivity due to the modification of the electron density of Ni metal, It has been established that the addition of K modified the electron density of Ni metal, and this result is ascertained by a shift of the Ni binding energy in XPS measurement and Ni absorption edge in XANES spectra.