Avian influenza viruses represent a rising threat of pandemic influenza. Allantoic fluid including influenza virus H9N2 was run on downstream processing to purify the virus. To do this, allantoic fluid was clarified and concentrated. It was applied to size exclusion chromatography. Different parameters such as ovalbumin, protein content, and hemagglutinin activity were determined to confirm the purity. The results may suggest that this method is quite efficient for achieving a purified H9N2 influenza virus and further reveal that size-exclusion chromatography is a practical method for purifying avian influenza viruses. In conclusion, this procedure can be used in vaccine production and antiserum preparation as an alternative to traditional methods and also can be considered in the purifying of other viruses when there is no facility of ultracentrifuge or zonal centrifuge.