Abstract: Severe sediment deposition affects normal operation of reservoirs, but discharging flood water from them in flood season often causes a certain loss of power generation. Aiming at the problem of sediment deposition in reservoirs, this paper designs an unconventional flood-flushing method using reservoir regulation to flush away sediment during unconventional floods. Physical model tests are used to study the trends of sediment transport during symmetrical and asymmetric unconventional floods. Results show that under the symmetrical floods of a fixed average flow rate, the capacity of sediment transport is increased with the increasing flow amplitude, while under the asymmetric floods of fixed average and peak flow rates, it is increased with a decrease in the ratio of base flow duration to peak flow duration. Based on this, we develop a three-dimensional numerical model of hydrodynamics and sediment transport in the Jinping II reservoir, design a reasonable unconventional flood-flushing mode, and verify its effect on sediment flushing and deposition reduction. Thus, unconventional flood flushing is an effective method to reduce sediment deposition in reservoirs, helping save flushing water and achieving economic optimum.