Suspension polymerization was used to prepare PEG homopolymer particles with nanometer size. In order to achieve the optimized reaction conditions for producing the smallest nanosized particles, the effects of various reaction conditions such as sonication, monomer concentration, molecular weight of monomer, and stabilizer concentration on the size of PEG hydrogel nanoparticles were investigated. Among these reaction conditions, sonication and the molecular weight of the monomer affected significantly the size reduction of PEG hydrogel nanoparticles, that is, the particle size decreased as sonication was conducted and the molecular weight of the monomer decreased. PEG homopolymer hydrogel nanoparticles having an average size of 182.1 nm were finally obtained with optimized reaction conditions.