The laser Doppler velocimeter (LDV) and hydrogen bubble ow visualization techniques have been used to measure the characteristics of turbulent boundary layer ow over riblets surface and to observe its coherent structure in the near wall region. The experimental results indicate that, in comparison with the turbulent boundary layer ow over a smooth surface, greater values are obtained for the thickness of viscous sublayer, the thickness of bu er region and the integral constant C in the log-law. Moreover, the maximum value of turbulent intensity u0=U is increased by 6.7%, but its position is decreased by 6.4%, the skewness factor and the atness factor are hardly a ected by the riblets surface. The non-dimensional value of low-speed streak spacing is reduced by 20%, this is also an indication of turbulent drag reduction.