The dissociation of virus-like particles of Hepatitis B surface antigen (HBsAg) during the adsorption-desorption on the solid-phase of chromatography is a main challenge for its purification. Herein, poly (ethylene glycol) (PEG) was applied as an additive during the purification of HBsAg from recombinant Chinese hamster ovary (CHO) cell culture to improve the HBsAg recovery and protect its structural assembly. The presence of 1% of PEG10000 in the mobile phase of ion-exchange chromatography (IEC) of DEAE-Sepharose FF column could increase the recovery of HBsAg from about 55% to 80%, with a similar purification (-fold) (about 12) compared with the absence of PEG. Importantly, glycosylated protein forms of HBsAg were reserved well by PEG-accompanied chromatography. Furthermore, size exclusion chromatography-multiangle laser light scattering (SEC-MALLS) analysis was performed on line to monitor the aggregates, particle size and molecular weight distribution of HBsAg. The results demonstrated that the HBsAg particle size and assembly are more homogenous after adding PEG in the mobile phase of IEC than no PEG added in the mobile phase.