Abstract: The mean velocity distributions in turbulent boundarylayers of smooth surface and two different riblet surfaces are measured withIFA300 constant-temperature anemometer in low-speed wind tunnel to validatethe full development of turbulent boundary laye. Friction velocity and wallfriction stress of turbulent boundary layer are obtained with theleast-squares fitted curve of the sublayer velocity distribution based onSpalding formula, and virtual origin position of riblet surface can beacquired accurately. Moreover, the momentum loss thicknesses of these threeexperimental models is also calculated. The results show that the dragreduction effect is obvious in turbulent flows due to the riblet surfacewith the comparsion of the momentum loss thicknesses and wall frictionstresses of smooth surface and riblet surface.