Abstract: Whether at home or abroad,there is a problem that the actual power generation of wind farms located in complex terrain is lower than that calculated by CFD software. Therefore,it is necessary to improve the understanding of the characteristics and formation mechanism of wind resources in complex terrain and improve the numerical simulation method of wind resource for wind farm siting. For this purpose,wind resource characteristics observation experiments are carried out in southern Tibet,Hengduan Mountains and Shanxi Plateau,which represent the extremely undulating mountains and wide valleys,the extremely undulating mountains and deep valleys,as well as the medium and small undulating hills and mountains. Through analyzing the contribution of the atmospheric background wind field,local atmospheric circulation,terrain dynamic forcing,surface friction and thermal action to the formation of wind resource characteristics under different typical complex terrain conditions,the results are as follows:the role of local atmospheric circulation in Shanxi Plateau is relatively small,the valley wind circulation in the southern Tibetan valley and Hengduan mountain area plays a major role in the formation of their wind energy resource characteristics,especially in Hengduan mountain area,where there are multi-scale local circulations. The traditional CFD numerical simulation of wind resources for wind farms siting is not enough to describe such a complex wind field. Therefore,the numerical simulation method combining mesoscale and CFD is very necessary in the wind resource assessment for wind farm siting in complex terrain.