According to the Soil Pollution Prevention and Control Law, the decommissioning sites of nuclear facilities can be divided into three open scenarios - agricultural land, class I construction land and class II construction land. Relevant parameters (including soil density, contamination depth, effective porosity of contaminated soil, personal water intake, personal breathing volume, etc.) were selected for calculation. Based on the dose screening value of 0.01 mSv per year, the residual level in the soil was calculated and the main nuclide pathways were analyzed. The study provides the principle of determining soil residual radioactivity level according to different land use types and irradiation routes, so that the treatment target of contaminated sites is more scientific and detailed, and at the same time, the environmental management of the management department can be adjusted. Compared with the recommended values in foreign guidelines, the rationality and variety of residual radioactivity levels can provide technical support for the revision of "Regulations on Acceptable Levels of Residual Radio-activity in Soil of Proposed Open Sites (Provisional)" (HJ53-2000).