A coprecipitation method was developed to synthesize fibrous gamma-Al2O3 with a large pore volume using a membrane dispersion microreactor with NaAlO2 and Al-2(SO4)(3) as reactants. The pore size distribution was controlled because of the high mixing intensity and relatively homogeneous saturation in the membrane dispersion microreactor. The influences of the pH and concentration of the NaAlO2 aqueous solution and of the two-phase flow rates were investigated. By controlling the pH to be around 9 and the concentration of NaAlO2 aqueous solution to be 0.50-1.25 mol/L, we obtained gamma-Al2O3 nanofibers with pore volume of 0.95-1.52 mL/g. Under the maximal pore volume (1.52 mL/g), the specific surface area was 403.8 m(2)/g and the pore size distribution was 3-50 nm with a distribution variance of 0.2020. The length and diameter of the nanofibers were about 27.3 and 3.4 nm, respectively. This study provides a simple, economical method for preparing fibrous gamma-Al2O3 with both a large pore volume and a narrow pore size distribution, which could be used as an excellent catalyst support for the petroleum-refining industry.