The boundary conditions for the environmental dredging of urban braided rivers are complex due to poor water quality，complex flow patterns，serious siltation，and large numbers of river-crossing buildings. This paper proposes a concept that the design of the environmental dredging depth should unfold from the perspectives of pollution layer depth，riverbed evolution，and structure safety，and the concept involves the following three aspects：1）Controlling the dredging depth with the bankfull elevation is advisable at the compound section of a single river section. 2）for the stabilization of the riverbed，the design of the dredging depth presupposes controlling the proportion of the cross-sectional area and keeping the main channel consistent with the natural slope. 3）At dikes and structures，the design of the dredging depth should consider the influences of the safety distance from the dikes and structures and the scouring depth after dredging to excavate the polluted sediment to the maximum extent on the premise of stable riverbeds and safe structures. The proposed concept has achieved successful application to an environmental dredging project in a river section.