Abstract: According to the mechanical condition of incipient motion of the non-cohesive uniform sediments and using some results of other researches,the relationship between incipient probability and flow condition is established.The for mulae of incipient shear stress and incipient flow velocity in which the incipient probability has been taken into account is obtained,the incipient criterion has been connected with the incipient motion condition.The analysing of some typical formulae for incipient motion condition of non-cohesive uniform sediment shows that the formulae of this paper is rational.