Uncertainties, existing all along with food safety risk assessment, can be fallen into two broad categories. The first is related to the extrapolation of key data and the second is related to limited database. Uncertainty factor (UF) approach is the widely-used and typical method to deal with these uncertainties. Similar UFs in setting health-based guidance values have been recommended by many international or national bodies. Most of them recommended that fewer uncertainties in risk assessment can be processed by several developing methods, such as benchmark dose (BMD) approach and chemical-specific adjusting factor (CSAF) approach.