The pandemic of a newly emerging coronavirus (SARS-CoV-2), the causative agent of severe pneumonia disease , is a major global health threat. Epidemiological studies suggest that bats are the natural zoonotic reservoir for SARS-CoV-2, however, the host range of SARS-CoV-2 and the identity of intermediate hosts that may facilitate the transmission to humans remains unknown. Coronavirus-receptor interaction is a key genetic determinant of the host range, cross-species transmission, and tissue tropism. SARS-CoV-2 uses Angiotensin-converting enzyme II (ACE2) as the receptor to enter its host cells in a species-dependent manner. It has been shown that human, palm civet, pig and bat ACE2 can support virus entry, while the murine ortholog cannot. In this study, we aimed to characterize ACE2 from diverse species for its ability to support viral entry. We found that ACE2 is expressed in a wide range of host species, with high conservation especially in mammals. By analyzing critical amino acid residues in ACE2 for virus entry, based on the well-characterized SARS-CoV spike protein interaction with ACE2 (human, bat, palm civet, pig and ferret ACE2), we identified approximately eighty ACE2 proteins from mammals could potentially function as the receptor to mediate SARS-CoV-2 entry. Functional assays showed that 44 of these mammalian ACE2 orthologs, including domestic animals, pet animals, livestock animals and even animals in the zoos or aquaria, could bind viral spike protein and support SARS-CoV-2 entry. In summary, our study demonstrates that ACE2 from a remarkably broad range of species support SARS-CoV-2 entry. These findings highlight a potentially broad host tropism and suggest that SARS-CoV-2 might be distributed much more widely than previously recognized, emphasizing the necessity to monitor the susceptible hosts, especially their potential of cross-species, which could prevent the future outbreaks.