Chelerythrine was successfully micronized from methanol solution using Supercritical Carbon Dioxide (SC-CO2) as an antisolvent via the Solution Enhanced Dispersion by Supercritical Fluids through the Prefilming Atomization (SED-SPA) process. The morphology and particle size of the chelerythrine microparticles were visually analyzed by scanning electron microscopy (SEM). For the purpose of the optimizing operating conditions of the SEDS-PA process, the influences of the experimental variables, i.e., temperature, pressure, solution flow rate and initial solution concentration, on the particle size and morphology of chelerythrine microparticles are discussed in detail. The results show that the best process conditions for the micronization of chelerythrine are: T = 313 K, P = 20 Wa, C = 2.0 g/L and F = 2.0 mL/min. The precipitates obtained under the optimized experimental conditions are short rod-like chelerythrine microparticles with a mean particle size of 0.1-1 mu m in width.