A series of concludes have been obtained，through theoretical analysis, formulas derivation and parameters calculation based on analysis of the motion mechanism of non-uniform bed load. The minimum dimensionless critical shear stress value of non-uniform sediment has been obtained as 0.020. The formula for calculating the transport rate of bed load of non-uniform sediment has been proposed. The formula shows the transport rate is not a constant but varies with the relative exposure degree of particles that lying on riverbed when the flow intensity is at fixed value. The condition and formula for calculating the maximum diameter, dc max, of incipient sediment according to the minimum dimensionless critical shear stress value, θ0, of bed load at equilibrium condition has been put forward. And a formula for calculating the size distribution of bed load has been presented too. Results above mentioned have been verified with field or laboratory experimental data.
