Based on physical mechanism,a stochastic Fourier spectrum model of fluctuating wind speed with solid physical basis is proposed.In view of physical scene of atmospheric turbulence,relationship between the scales of vortex in turbulence and the subranges in energy spectrum is revealed.According to the exponential laws of Fourier spectrum in different energy ranges,a stochastic Fourier spectrum model is established.In actual physical process,the boundary wavelength lc of the two subranges corresponds to the boundary value of the scales of vortexes in energycontent range and in equilibrium range.Essentially,lcis a variable and the main physical factor which affects its value is the ratio between shearratio of the mainflow and vorticity of turbulence.It is found that the ratio is proportional to shearratio.Along with numerical calculation,the formula to calculate lc and the other parameters in Fourier spectrum model is founded.Finally,taking ground roughness length and 10 min mean wind speed as two basic variables and turbulence intensity as related variable,the distribution of lc and the normalized stochastic Fourier wavenumber spectrum with the bilinear characteristic can be obtained.The theoretical results accord with the measured results well.