The NiAlO (x) and NiSiO (x) complex oxides with high surface areas were prepared by the co-precipitation method through the control of acidity of solutions. Nickel species were found to be highly dispersed in these complex oxides and a remarkable feature was that the incorporation of large amount of nickel cations into SiO2 generated the great amount of surface acid sites. Upon the sulfidation by CS2, the sulfided catalysts were found to be highly active for the conversion of 1-hexene to different products formed from the three main competitive reactions (skeletal isomerization, double bond isomerization and hydrogenation of all hexenes). The high yield of skeletal isomerization of 1-hexene on a sulfided NiSiO (x) (55 %) could be attributed to the high density of acid sites for the adsorption of 1-hexene as well as the low hydrogenation activity of nickel species on this catalyst. In contrast, the high yields of direct hydrogenation and double bond isomerization of 1-hexene on the sulfided NiAlO (x) might be due to the high hydrogenation activity of nickel species as well as the surface acidity and basicity on the catalyst. The sulfided NiAlO (x) and NiSiO (x) complex oxides were highly active for the conversion of 1-hexene to different products. The high yield of skeletal isomerization of 1-hexene on the sulfided NS10 (55 %) could be attributed to the high density of acid sites for the adsorption of 1-hexene. [GRAPHICS] .