Objective Increasing number of human infection caused by the novel avian-origin H7N9 subtype influenza virus underscores the need to better understand the pathogenesis and transmissibility of this virus in mammals. Methods Mice inoculated with H7N9 influenza virus and put into the cage with naive mice, which were then specifically measured their clinical signs, virus shedding, tissue dissemination and pathology. The secretion from the cohabitant mice was inoculated to other normal mice to analyze the possible transmission routes. Results H7N9 influenza virus replicated in the lung, intestine and brain of the experimental mice. It was worth noting that H7N9 virus could transmit between mice in close contact by mucosa and fecal-oral routes, with the highest concentration of virus found in pharyngeal secretions. Conclusions Our results demonstrate that the avian-origin H7N9 subtype influenza virus can infect mice without adaptation and spreads by mouse-to-mouse transmission. The secretions of infected mice are source of infection for mice in direct contact, and it is similar to the influenza virus transmission between humans.