The hydrodynamics in a gas-solid airlift loop reactor was investigated systematically using experimental measurements and CFD simulation. In the experiments, the time averaged parameters, such as solid fraction and particle velocity, were measured by optical fiber probe. In the simulation, the modified Gidaspow drag model accounting for the interparticles clustering was incorporated into the Eulerian-Eulerian CFD model with particulate-phase kinetic theory. Predicted values of solid fraction and particle velocity were compared with experimental results, validating the drag model and the simulation. The results show that the profiles of particle velocity and solid fraction are uniform in annulus. However, the core-annulus structure appears in other three regions (draft tube region, bottom region and particle diffiuence region),which presents the similar heterogeneous feature of aggregative fiuidization usually occurred in normal fiuidized beds. Simulated profiles of panicle residence time distribution indicate that the airlift loop reactor should be characterized by near perfect mixing.