Abstract: Taking fluctuating wind speed as example, this paper displays the basic method of modeling the structural dynamic excitation based on physical process. According to classic turbulence theory, the physical laws of inertial sub-range and shear sub-range in homogeneous shear turbulence are described. Along with the basic idea of physical stochastic system, a normalized stochastic Fourier wave-number model with simple format is established. The probability distribution of the boundary position of the shear sub-range and inertial sub-range is obtained by the Probability Density Evolution Method (PDEM) and the probability distribution of the basic variables including ground roughness and 10-min mean wind speed are also obtained. The research shows that the mean spectrum of the theoretical prediction based on the physical process corresponds with the measured Fourier mean wave-number spectrum well. The model proposed here is expected to provide a reasonable excitation model for wind-resistant design and reliability analysis of structures.