Objective To investigate the molecular epidemiologic characteristics and genotypes of norovirus in children less than 5 years of age in Lulong area from 2008 to 2009.Methods 325 stool specimens and epidemiological data from hospitalized children with diarrhea less than 5 years of age were collected.Rotavirus was detected by using the ELISA kit.Norovirus,adenovirus and astrovirus were detected by multiple reverse transcription-polymerase chain reaction (RT-PCR).Partial norovirus strains were sequenced and the tree was conducted by using the phylogenetic analyses.Results Norovirus was detected in 37out of 325 (11.3％ ) specimens,ranked only second to rotavirus (48.6％),and higher than adenovirus (6.5 ％ ) and astrovirus (4.3％).Norovirus predominantly infected children less than 2 years of age and the season peak of norovirus occurred in November.Phylogenetic analysis showed that the predominant strain was the GⅡ.4/2006b variant.Interestingly,a novel unreported GⅡ-4 variant was found in this study.Conclusion Norovirus was one of the most important pathogens causing acute gastroenteritis from 2008 to 2009 in Lulong area.The GⅡ.4/2006b vairant was still the predominant strain.It is important to keep on monitoring the novel GⅡ.4 variant.