Abstract: Abstracts: Objective To observe the changes of chickens when post-challenge with LPAIV H9N2. Methods One-month-old SPF chickens were inoculated with 107.4EID50/0.1ml H9N2 viruses, 0.5ml/chick. Results Chickens were sick and a few of them were died. At necropsy, the primary gross lesions in all chickens were severe pulmonary consolidation and multifocal hemorrhage in several organs, including subcutaneous, lung, heart, thymus, stomach, intestine, liver, and lymph nodes; Necrotic foci were in liver, spleen, kidney and lung. The bacterial isolated was identified as Pasteurella multocida based on biochemical characteristics and PCR. Conclusion Low pathogenic avian influenza H9N2 virus may cause secondary infection of Pasteurella multocida, which could results of high rate both morbidity and mortality in chickens.