On November 26, 2021, World Health Organization (WHO) designated the B．1.1.529 variant firstly reported in South Africa as a variant of concern (VOC) of SARS-CoV-2, named Omicron. There are about 50 mutations in this variant, and at least 30 mutations in the spike protein region alone, which far exceeds the number of mutation sites in other endemic strains. The analysis on mutated sites and preliminary experiments confirmed that the variant may be highly contagious and associated with immune escape. How Omicron variant will affect the pandemic has aroused wide public concern in various countries. This review focused on the basic characteristics, detection, pathogenicity, infectivity, and immune escape of Omicron variant.