［Purposes ］ The influence of terrain boundary effects on the numerical simulation accuracy of multi -scale coupled wind fields over complex terrain was investigated to solve the problem of large simulation errors caused by unreasonable inlet boundary settings，providing data support for wind energy resource assessment and wind farm site selection in complex terrain.［Methods］ With a complex mountainous wind farm in southeast Guizhou as the research object，a multi -scale coupling method of a mesoscale meteorological model and computational fluid dynamics was adopted.The simulation results of the mesoscale meteorological model were subjected to spatial and temporal downscaling treatments and then used as the inflow boundary conditions for computational fluid dynamics.Six groups of combined working conditions with different horizontal inlet boundary lengths and inlet terrain relief characteristics were designed.Combined with measured data，the reliability of the simulation results was verified through indicators such as mean absolute error and root mean square error.［Results］ The near -ground wind field is sensitive to the horizontal inlet boundary length and the inlet terrain relief characteristics，and the wind field differences in the upstream area are significant.As the height and computational distance increase，the influence of terrain variables on the wind field weakens，and the wind field distribution tends to be consistent.A moderate horizontal inlet boundary length within the range of several kilometers promotes the convergence of wind field simulation errors.The reliability of simulation results is higher under the working condition with gentle terrain and a small negative slope weight in the inlet area，and the simulation accuracy of the optimal working condition is significantly higher than that of the traditional mesoscale meteorological model.［Conclusions ］ The horizontal inlet boundary length and the inlet terrain relief characteristics are key factors affecting the simulation accuracy of multi -scale coupled wind fields.Reasonable optimization of terrain parameters effectively improves the simulation accuracy of wind fields over complex terrain.The research results have practical significance for wind energy resource assessment over complex terrain.