A new two-phase atomizer used in the fluid catalytic cracking (FCC) process which has recently been studied experimentally, is modeled in three dimensions in a lagrangian framework by using a computational fluid dynamics (CFD) method. Special emphasis is placed on the study of the liquid atomization. The atomizer is used to quantitative tests in an air-water cold system in combination with a particle dynamics analyzer (PDA). Linearized instability sheet atomization (LISA) model is employed to simulate the water atomization process. The effects of the distance from the nozzle outlet on the droplet size and velocity distribution in the downward spray are studied. Predictions of droplet diameters, trajectories, and velocities are made and they are compared with relevant experimental results; the predictions and results are found to be in good agreement.