Abstract: The calculation formulas of the resistance coefficient in open channel flows were summarized according to different flow patterns and flow regions. On the basis of the actual experimental data and by using the different calculation formulasas well as from the theory of uniform flow in open channel, the flow capacitiesof the openchannel were calculated respectively. The calculated discharges arecompared with the measured discharges, the relative errors are between -7.9%and 2.6%,but the errors obtained from the formulas of index form and logarithem form are smaller(between -2.0% and 2.68%).With a given roughness factor,the differences of the resistance coefficients calculated using different resistance calculation formulas are small.Considering the engineering application and calculation convenience,the formula of indexform has a better adaptability,and calculated precision mainly depends on the selection of roughness coefficient n.Employing rough region formulas to calculate the discharges of transition rough region still have better results.