The highly dispersed Ru catalysts supported on Al-SBA-15 with different Al/Si ratios were prepared by the “two solvent technique” and tested in Fischer–Tropsch synthesis. TEM and N2 adsorption–desorption results illustrated that Ru crystallites were uniformly embedded inside the pore channels. XRD, hydrogen temperature programmed desorption and O2 titration results showed that the dispersion of Ru increased with the increasing Al/Si ratio. The XPS results indicated that the interaction between Ru and the supports was a function of Ru dispersion, a stronger metal-support interaction was found in the catalyst with higher Ru dispersion. The selectivity of olefins was increased by increasing Ru dispersion. When the dispersion reached 86 %, this tendency was more pronounced and the selectivity of C2–C4 hydrocarbons remarkably increased to 27.0 %, with very high percentage of olefins (62.7 %).