The SO₂ instantaneous Concentration in the Dachangdistrict of Nanjing under neutral conditions is calculated by using the Gaussian (normal) model, the Egan model, the SCIM model and the GCEM model. The re suits from calculation are compared with the observational data. It is found that the GCEM model for which the terms of topography revision and chemical decay have been taken into account works well and its calculated values are consistent with recorded concentrations.