An antisolvent processing technique by simultaneous compressed antisolvent precipitation and photopolymerization for cross-linked polymer microparticles formation was presented in this paper. In this process, photopolymerization of the homogeneous solution composed of methylene chloride, poly(ethylene glycol)600 diacrylate (PEG600DA) as monomer and diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide (TPO) or 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator resulted to microparticle when it was sprayed into supercritical carbon dioxide (scCO2) and simultaneously exposed to initiating light. High miscibility of the solvent in scCO2 made methylene chloride quickly extracted from the dispersion phase, leaving very high concentrations of monomer (PEG600DA) dispersed in scCO2. The high monomer concentration combined with photo initiating polymerization facilitates rapid reaction rates and ultimately lead to polymer precipitation. Particle size and morphology were adjustable by changing the processing conditions, such as temperature and pressure. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012