The hydrodynamics of a two-dimensional airlift reactor (32 x 100 x 1.2cm) in the dispersed bubbling regime is investigated through experimental measurement using particle image analyzer (PIA) and numerical simulation using computational fluid dynamics model. The instantaneous and the averaged hydrodynamics in the dispersed bubbling regime have a similar flow structure: (1) a global circulation flow with an upstream in the riser and a downstream in the downcomer, (2) two pairs of vortices, one at the bottom sidewall of the riser and the other at the upper edge of the draft tube in the downcomer. The bubble streams rise roughly rectilinear with relatively uniform bubble size along the column and generate small-scale vorticities in between bubble streams. The bubble wake drifting and the circulation cause the averaged vertical velocity is relatively large than the averaged horizontal velocity for all locations. Due to the fluctuation of the vortices, the averaged normal stresses at bottom and upper locations are higher than those at middle location. A numerical simulation with the Eulerian-Eulerian two-phase model has been carried out using a commercial code, CFX4.4. A satisfactory agreement between the simulated and the measured results has been accomplished, although few slight discrepancies might have been found in the liquid velocity distribution.