To further improve the efficiency of grid-generated turbulent wind field for large eddy simulation （LES）， an improved turbulence generation method based on LES is proposed in this paper， in which grid-jet can be obtained on the inlet boundary. Then， LES of the flow around a circular cylinder at Re=3 900 is successfully carried out. The results indicate that the turbulent wind field generated based on virtual grid exhibits isotropic characteristics. The turbulence intensity decreases exponentially along the flow direction， and the turbulence integral scale increases linearly along the flow direction. The fluctuating wind power spectrum is consistent with the von Kármán spectrum. In addition， compared to a smooth inflow， the mean drag coefficient of the cylinder decreases in the turbulent inflow， whereas the standard deviation of the drag coefficients and lift coefficients increase significantly， indicating stronger pulsations of the lift and drag forces in turbulent flow. Turbulence also delays flow separation on the cylinder surface and inhibits separation， resulting in a shorter recirculation length and a lower Strouhal number. Vortex shedding becomes unstable and the shedding energy is stronger.