The roughness for heat(by the way of excess resistance κB^-1) over desert and Gobi sites have been calculated in HEIFE area.It was found that the range of κB^-1 at individual sites were large.A test of the utility of the excess resistance based on the calculated κB^-1 showed that ignoring of this resistance which came from the difference between the roughness length for heat and momentum will result in largely overestimation for sensible heat flux.A preliminary conclusion can be drawn that it would be unproper to take the hypothesis of z_0m=z_0h when estimating sensible heat flux using a resistance-type method.