In the Sagaut mixed-scale model,an improved subgrid-scale(SGS) characteristic length,representing the scale of local energy-containing SGS motions,is proposed.Large-eddy simulations(LES) at temporal mixing layer and neutral atmospheric boundary layer indicate that by the improved SGS characteristic length,satisfactory spatial distribution of the SGS motions can be obtained and are closer to the results of direction numerical simulations(DNS).Compared with the basic model,the modified model with the improved SGS characteristic length produces more accurate mean quantities and turbulent statistics.The results demonstrate its valuable and wide application to LES.