Abstract: Based on the analysis of the main reasons that lead to the error problems appearing in the operation of the CAPPS Model System in Taiyuan City, the varying of the orographic background fields were discussed. According to different seasons and different synoptic situations, the accommodation function of complex error coefficient and raising dust coefficient is added to this model system and various numerical simulation experiments are made. The result shows that through the simulation experiment schemes based on error analysis, the correlation coefficients of the prediction and the observation of main pollutants: SO₂, NO_x and PM₁₀ are increased to 0.96, 0.91 and 0.89. The forecast accuracy of the CAPPS Model System localized into an operation numerical model system in Taiyuan City can be reached to 90%.