Abstract: COVID-19 has emerged around the world since December 2019 and rapidly evolves as a major global public health challenge. SARS-CoV-2 is a positive single-stranded RNA virus with a relatively high natural mutation rate. The emergence of SARS-CoV-2 variants is generally considered as the outcome of a “mutation-selection-adaption” process. The enzyme APOBECs that is activated in the inflammatory microenvironment may facilitate viral mutagenesis. Currently， the major SARS-CoV-2 variants that impose public health significance are B.1.1.7， B.1.351， P.1， B.1.6.7.2， B.1.1.529 and so on， with probably increasing transmissibility， decreasing reactivity to the neutralizing antibodies， immune escape， and enhancing disease severity and mortality. Consequently， it warrants up-to-date countermeasures against evolving SARS-CoV-2， including tracing viral mutagenesis， developing vaccines against major variants， and enhancing social distancing.