Noroviruses are regarded as the leading cause of epidemic gastroenteritis all over the world, with a wealth of genetic diversity. And GII. 4 is regarded as the predominant strain, which has constantly infected humans attributed to a fast rate of evolution in the past two decades. With the discovery of virus binding-receptor and understanding of immune specificity, the research of evolution mechanism of the virus has been continuously developed recently. It has been hypothesized that the receptor switching and antigenic drift maintains GII. 4 persistence in human populations. Also the RNA viruses, high mutation rate and the limited space of genomic variation have also affected the direction of norovirus evolution.