Abstract: In order to study the distribution law of Shields curve in laminar regime, the critical tractive force for the onset motion of uniform non-cohesive glass beads is investigated based on the CCD (charge coupled device) imaging technology combined with laser scanning and computer image processing technology, using a mixture of water and glycerol. According to the laminar flow theory, the rolling model for the onset motion of non-cohesive particles is established and an equation for non-dimensional critical tractive force is derived. Experiments show that the particle Reynolds number versus Shields number is a systematic band distribution in the laminar region; further, fluid flow induces bed armoring and leads to the decrease in particle protrusion on the granular surface, the critical tractive force can be doubled consequently. This indicates that the structure of the granular surface has a significant impact on the critical tractive force for the onset motion of particles, and band distribution is a characteristic of Shields curve in the laminar regime.