Objective To investigate the prevalence of Norovirus in oysters cultured from farms, markets and restaurants, and to assess the foodborne disease risks. Methods Real-time reverse transcription polymerase chain reaction (RT-PCR) method was used to detect Norovirus RNA in oysters from farms, markets and restaurants. The semi-quantitative risk assessment for Norovirus in oysters was made by Risk Ranger. Results The overall detection rate of Norovirus in the 480 oyster samples was 11.04% (53/480). The detection rates of Norovirus in oyster samples from farms and markets were 15.83% (38/240) and 12.50% (15/120), respectively. No Norovirus was detected in oyster samples from restaurants. All Norovirus detected were genogroup Ⅱ(GⅡ). The relative risks for Norovirus caused by eating processed oysters and raw oysters were 44 and 67, the probabilities of illness caused by oyster per day per consumer of interest were 3.29×10-6 and 3.29×10-2, and the total predicted patients per annum of interest were 3.10×10³ and 3.10×10⁷, respectively. Conclusion The result highlight a high prevalence of Norovirus GⅡ contamination in oysters from farms and markets in Guangxi. Avoiding eating raw oysters and processing before eating are all effective method to decrease Norovirus infection.