With the expansion of urban area and growing urban groups, cross-city pollution is becoming increasingly serious, and more concerns have been raised over this issue. This study defined the concept of atmospheric environmental safety distance index (AEI) as an indicator of cross-city pollution and built an optimization model to quantify the environmental safety distance. The model consists three components:(1) pollution reduction, (2) adjusting pollution source location, (3) optimizing land use. In the case study, the model was applied to H area, to calculate 5AEIs related to H in two scenarios of different pollutant emissions of SO₂ and NO_x in a base year. Results showed that AEI between H and K is larger than 1, indicating the presence of cross pollution between these two areas. Results from optimization indicated that the AEI can be reduced to 1.0under the emission reduction scenario when pollutant emissions for SO₂ and NO_x would be reduced by 62.3% and 63.7% respectively. The adjusting pollution source location scenario showed that the location should be moved to southwest, and AEI for SO₂ and NO_x could be reduced to 0.15~1.00 and 0.17~1.00. Optimizing land use can reduce AEI though fails to meet the target. Moreover, the AEI between H and K could be reduced by 8.8% and 0.9% for SO₂ and NO_x respectively.