To understand and grasp the impact of the planned project on the atmospheric environment of Yumen City and the surrounding counties and cities after its completion, the WRF-Chem model method was used to study the PM2.5 and O3 concentrations in Yumen City after the completion of the project. Two scenarios were predicted. Scenario One, where the total amount of waste gas generated in the industrial park after the completion of the project is 3127.75 t/a, and Scenario Two, where the total amount of waste gas generated is 5112.74 t/a. The model simulation results indicate that during the planning period, the 8-hour average concentration of O3 at each environmentally sensitive point, when added to the current concentration, meets the standards under the guaranteed rate. Under Scenario One, both the daily average and annual average concentrations of PM2.5, when added to the current concentration, meet the standards. Under Scenario Two, the daily average and annual average concentrations of PM2.5 at the boundaries of the Mahuangtan core area, Mahuangtan buffer zone, and the experimental area of the Nanshan Nature Reserve exceed the standards when added to the current concentration, while other sensitive points meet the standards. To meet the control targets of the planning area, it is recommended to implement stricter pollution source reduction measures to ensure continuous improvement of PM2.5 concentrations.