Abstract: Numerical stability is one of the most important factors in Computational Wind Engineering. It has great effects on the accuracy of numerical prediction of mean wind pressures on the complex large-span roofs. Two different ways are used to stabilize the numerical oscillations in predicting the mean pressures on large-span roofs: artificial viscosity techniques and low-order upwind scheme. By comparing these numerical results with wind tunnel experiment data, it could be found the results from artificial viscosity techniques agree better with experimental data. So artificial viscosity technique could be an effective way to improve the accuracy in predicting mean pressures on the complex large-span roofs.