Abstract: The present paper describes the investigation of polystyrene gel. The conversion and the distribution curve of gel and sol were measured, during the pore-forming process. It was found that earlier phase separation leads to a decrease in pore volume and strength of the resin. On the basis of this point, we proposed that the nonsolvent was added to adjust the pore volume and pore diameter when the resin became plastic and viscous, and designed a series of experiments.