In the paper we compared several formulas on the magnitude of concentration of monthly strem runoff and siltload within a year in 33 hydrological stations of tributaries of Yellow River in North Shaanxi Province. The reultsshiow there is a retoarked significance ralationship(α=0. 00 1 ) between Aggregation Index(Ag )

Gibbs-Martinsegregation Index(G. M)

Degree of concentrationCn) and Uneven Distribution Coefficient(Cl )which representthe characteristcs of concentration of monthly precipitation

strem runoff and load. Among the four formulas it is themaxmum that variation coefficient and the range of maxmum and minimum of theDegre of concentration(Cn).There is a remarkable significance relationship between yearlyload modulus or yearly runoff and monthly Degree ofconcentration and it's peried of which calculated from vector composition of monthly runoff or load as a vector.So

wecan use the indexes of monthly concentration characteristics to analvxis the stream runoff and sediment vield andto plan approaches of soil and water conservation in a watershed and realignmet of runoff and sediment