Abstract: Shields diagram is an experimental curve which describes the bed shear stress for the grains of sediment in critical condition. In this paper two formulae are given in the hydraulic fully rough state according to the result of Shields experiment. One formula is about the critical velocity for the grains of sediment which can be written in theform:U_c=√(0.12)/(λ)√((ρ_s^-ρ)/(ρ))gd,while another can be described as the following equation:λ=0.0917((d)/(H))^(1)/(3) They are very useful because they can be used to compute the criticalvelocity of thegrains of sediment and Dercy resistance parameter. This paper analyses the relationships among the results of these formulae and other related ones. The author discovers that they are in good accordance with one another.