Abstract: Based on the particle image velocimetry (PIV) and particle tracking velocimetry (PTV), velocity distributions of both fluid and particles were measured in a horizontal smooth pipe with a diameter of 10.15 cm and particles with a diameter of 250 μm. The interaction mechanism between solid and liquid phases at high Reynolds numbers was investigated. The range of viscous Stokes number taken is 0.96~5.93, the volume fraction of particles is 0.022%, the density ratio of solid to liquid is 1.05, and the maximum friction Reynolds number is 2 081, corresponding to a Reynolds number of 86 366. The experimental results indicate that the maximum particle number density is located at y/R = 0.45 in the lower-part pipe, induced by the effects of particle settling and turbulent ejection. In the upper part, the particle number density gradually increases from the upper wall to the pipe centerline. The presence of particles decreases the vertical fluctuating intensity velocity, thereby reducing turbulent activity. However, it has a negligible effect on the streamwise mean velocity and fluctuating intensity. The lower part of the pipe has a higher number of particles compared with the upper part, resulting in more turbulent attenuation in the lower part. With increasing Reynolds number, the particle-induced stress increases and more momentum transfers from the liquid phase to the solid phase, resulting in a decrease in turbulent Reynolds stress and an increase in viscous stress, which is associated with more turbulent attenuation.