Based on the wind parameters measured in the wind tunnel test, the wind field of Hangzhou Bay Bridge was simulated by improved harmonic synthesis method. The wind parameters involved in wind field simulation mainly include pulsating wind spectrum and spatial correlation function, and the wind field parameters in the wind tunnel are measured and combined and applied to the wind field simulation. The harmonic synthesis method to simulate the wind field of long-span bridges takes too long and is inconvenient to apply, and the improvement of harmonic synthesis method by Lagrange interpolation method can greatly improve the wind field simulation efficiency, and the wind field simulation flow chart based on the improved harmonic synthesis method and the corresponding program Improved-WAWS are compiled, which provides a practical method for wind field simulation of long-span bridges. The experimental results show that there is a certain difference in the attenuation factor λ at different spacing D, and the attenuation factor increases with the increase of wind speed U. The power spectrum, mutual power spectrum, correlation function and cross-correlation function of the wind speed sample time history simulated by the improved harmonic synthesis method are in good agreement with the corresponding target values.