A series of ordered mesoporous silica (OMS) SBA-15 supports with different morphologies were prepared by different synthetic methods to investigate the effect of the characteristics of the morphology of OMS on the ethylene dimerization outcomes. After additions of Ni and Al species into the SBA-15 support, a dimerization reaction of ethylene was performed using a fixed-bed reactor. Rod-type Ni-Al-SBA-15 with a small micron size showed better catalytic performance compared to those of the other catalysts. From these catalytic results, the particle size and morphology of a SBA-15 support critically influenced the catalytic activities and lifetimes of the dimerization catalysts. The optimum reaction pathway in the Ni-Al-SBA-15 catalyst enhanced the overall catalytic performance due to the suppression of the further oligomerization of ethylene and butenes. Moreover, ethylene dimerization was investigated over the rod-type Ni-Al-SBA-15 catalyst to discover an optimum reaction condition. The maximum yield of butenes was 24.7% at 300 °C at 11.5 bar with a WHSV of 1.5 h-1.