For the duct-ventilated highway embankments in permafrost regions of the Qinghai-Tibet Plateau, the cooling capability of duct-ventilated embankment enhanced by a self-windward vent is focused. Based on the intake-air volume in the ventilation pipe, the factors influencing the cooling capability in duct-ventilated embankment enhanced by a self-windward vent are analyzed. The analysis results indicate that the enhancement of the cooling capability in the duct-ventilated embankment with a self-windward vent is significant during winter months. For the self-windward vent equipped on the top of the vertical pipe, the cooling capability during winter months in the embankment increases with the increase of vertical pipe height. Convective heat transfer is a dominant mode of heat exchange between the ventilation pipe wall and the ambient air in the duct-ventilated embankment. From a convective heat transfer point of view, the height of self-windward vent installed ought to be as high as possible. However, due to disturbance of the wind field near both sides of the duct-ventilated highway embankment caused by the running vehicles, the height of self-windward vent shouldn’t exceed the embankment height.