Abstract: The Olympic regatta is the only performance in the Olympic Games which is the natural winddriven competition event. The wind in Qingdao in August (the Beijing 2008 Olympic Games period) is the weakest of the year, and the weak wind often impedes the sailing competition. However the weak wind in Qingdao is tied up with the development of landsea breeze. The background conditions for the land-sea breeze development in the Qingdao Olympic sailing venue are analyzed, and simulated with a highresolution numerical model. The results show that the background surface wind, the radial wind in the middle-upper planetary boundary layer (PBL), and the surrounding terrain and land-sea distribution, all affect the development of land-sea breeze in this area. Under clear sky, the surface conditions, including west wind, weak north wind, east wind and equable pressure field, as well as weak north wind in the middle-upper PBL, are all conducive to the development of sea breeze in the competition venue. However the surface conditions of south wind (either strong or weak) and strong north wind, the strong south wind and north wind in the middle-upper PBL, are all unfavorable to the development of sea breeze. However, when the surface wind is from the northeast, the blocking and decreasing of surface wind due to the upstream the Lao Mountain are favorable to the development of sea breeze. When the surface wind is southerly, the air flow in the area of sailing venue is bifurcated by the Lao Mountain and the Fu Mountain, and this effect is enhanced by the lateral sea breeze jet (southeast wind) developed in the Kiaochow Bay and the Lao Mountain Bay, resulting in the weak wind in the sailing venue. The above results have been successfully applied to the meteorological services for the Qingdao Olympic and Paralympic sailing competitions.