Objective To establish a guinea pig model of influenza A /California /7 /2009(CA7) virus infection and evaluate the intervention with hormone methylprednisolone for viral pneumonia due to this infection. Methods Female Hartley strain guinea pigs ( 200-300 g ) were divided into four groups: control，model，methylprednisolone group 1 and methylprednisolone group 2. The animals were anesthetized by inhalation of ether and inoculated intranasally inoculated with 0. 3 mL of virus CA7. Methylprednisolone was administered beginning at postinfection day 3 or 5，recommended dose lasting for 3 days and then quarter of recommended dose for another 3 days. The animals were observed daily for 14 days for clinical signs of infection and survival. Results The guinea pig model for A /California /7 /2009(CA7)virus infection was established successfully. The lung inflammation of methylprednisolone group 1 was alleviated compared with that of both model group and methylprednisolone group 2，but the survival rate was lower compared with that of both two groups. The lung inflammation of methylprednisolone group 2 was alleviated in comparison with that in the model group but aggravated compared with that of methylprednisolone group 1，while the survival rate was not affected. Conclusion Guinea pigs can be infected with influenza A virus A /California /7 /2009，and it is better to administer methylprednisolone on dpi 5 than dpi 3.