Abstract: OBJECTIVE To study on the micromization process of celecoxib which was carried on with an air jet mill, and to investigate its in vitro drug dissolution behavior. METHODS The micromization process parameters were optimized by Box-Behnken Design of response surface methodology (RSM) of grinding pressure(X₁, psi), pushing pressure (X₂, psi) as independent variables and particale size D50(Y₁, μm), D90(Y₂, μm) as dependent variables. The optimized micromization celecoxib was characterized for particle size and morphology. The dissolution rate and the dissolution amount of micromization celecoxib, reference formulation, and API were determined and compared. RESULTS Particle size of micromization celecoxib was found to be D₅₀ 1.07 μm, D90 3.71 μm. And the micromization celecoxib was found to be small and homogeneous as seen in scan electron microscopy. The in vitro accumulated dissolution of micromization celecoxib was higher than that of the API. CONCLUSION The Box-Behnken experimental design used to optimize micromization process of celecoxib by air jet mill was simple and practical.