Abstract: As an important parameter, the bankfull discharge is morphologically significant in the study of river morphology, sediment motion, flood dynamics and their ecological impacts. Previous researchers have pointed out that the determination of bankfull discharge is more relevant at river reach scale than at a local scale. Based on the geometry data obtained from the lower Wei River, in this paper we analyze the variation of bankfull discharge at reach scale (QBFR) in fluvial process. To identify the bankfull elevation of each cross section, we adopted a method of Wolman (WOL) that is based on the surveyed cross-sections and geometric criterion. The method of convergence was used to calculate QBFR. The analysis result indicates that the QBFR of this river reach is well correlated with its inflow discharge and sediment conditions. Besides, according to the length of convergence that depends on the fluvial processes, field observations of QBFR should be extended in order to improve its identification.