Coronaviruses generally infect their natural hosts but scarcely infect other species of animals. The interspecies transmission of coronaviruses depends on the interaction of spike protein with the receptor. Receptor binding domains as well as other domains in spike proteins are mainly related to the tropism of coronaviruses. The emergence of new and host-across strains of coronaviruses is due to the huge RNA genome, specific subgenomic RNAs and high recombinant rate between RNAs. And both persist infection and co-infection provided the opportunities for the recombinant events and sequential host-shifting.