Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant was first detected in Botswana and subsequently led to a worldwide surge in infections. Until now, Omicron and its lineages, the most highly mutated strains among variants of concern (VOC), have contained at least 50 mutations in the entire genome. Mutations give the virus certain adaptive advantages, such as the enhanced affinity between receptor binding domain (RBD) and human angiotensin-converting enzyme 2 (ACE2) receptors leading to enhanced transmission of the virus, and the weakened ability of virus replication leading to mild symptoms in patients with COVID-19. In addition, given its high environmental stability, Omicron can partially escape the host immune response induced by vaccination or prior infection, and is highly resistant tomost therapeutic antibodies.In this paper, key mutations, virological characteristics, pathogenicity, and immune escape of the Omicron variant are summarized, in order to provide scientific reference for coping with the new situation of the pandemic, as well as improving pandemic prevention and control strategy and public health measures.