Abstract: The investigation on meteorological and micro-topography disasters of transmission lines shows that,due to the influence of col,windage yaw flashover and tower failure occurr fre-quently in the mountain region.However,studies on the topography formed by double three di-mension hills are relatively rare,and thus the distribution law of wind profile at different loca-tions is still indefinite.Under this situation,some wind tunnel tests about four types of col mod-el with different hill slopes and different valley widths are carried out.Then,on the analysis of wind tunnel test results,the influence law of some geomorphic features such as hill slope and val-ley width on wind profile is researched in this paper.Finally,some conclusions are derived as fol-lows.Compared with flat land,the degrees of wind speed-up at valley axis and hill peak reach 33% and 53% respectively,which are higher than the 10% stipulated in regulation,tending to cause more windage yaw flashover or tower failures.The wind speed at the valley axis will in-crease with the increasing of hill slope,and decrease with the increasing of valley width.Further-more,an equation matching this regularity is offered.At the valley axis of the col model,the wind speed-up effect of the downwind is a little stronger than the upwind,that may be caused by flow separation and more intensive fluid huddled at the downwind.At the hill peak,col features basically have no influence on the wind speed,so that the wind speed correction coefficients ob-tained by wind tunnel test display a good agreement with those obtained by fitted equation for so-lo hill.Since the wind speed correction coefficients at the hill peak are higher than those at the valley axis,in design the wind speed correction coefficients at the hill peak can be conservatively utilized for the whole col.