Avian influenza such as H5N1 could infect humans and cause great health concern due to its high mortality rate. In March 2013, a novel reassortant avian-origin influenza A (H7N9) virus was found in several patients with severe respiratory illness in China. Since then, at least 82 people in China have been infected with this new virus and 17 have died from this virus. The question of how these people were infected with this virus and whether this virus will spread among people remains an urgent topic for research. This study took an early investigation of this virus  by comparing the collected viral genome sequences  of 2013 H7N9 inChinaagainst those of previous avian H7N9 and examined the receptor binding specificity of this new virus. This virus was found to be very different from the previous avian H7N9 viruses and surprisingly many of the internal proteins of 2013 H7N9 from the avian and human hosts in China were either identical or similar. Our analysis of the HA protein of this virus implied that the current strains of 2013 H7N9 inChina displayed avian type receptors as their primary binding preference and human type receptors as secondary. For pandemic risk assessment, we also detected 23 mutations, including a few well known for host adaptation, in the HA1 domain of the HA protein from this virus. Each mutation was quantified for its impact on the recaptor binding selection using a bioinformatics approach. Collectively these current mutations tended to decrease the HA binding affinity for avian type recaptors and increase that for human type receptors, which could enhance the ability of this virus to infect humans.