Abstract: Excessive suspended sediment and high level supersaturation of total dissolved gas (TDG) often exist in the downstream water of a dam that is releasing flood. This threatens the survival of fish inhabiting in the water and is becoming an increasingly prominent eco-environmental issue that attracts more attention. This study conducts an acute exposure experiment and has investigated the combined effect of TDG supersaturation and sediment on rock carp (Procypris rabaudi). One-year-old rock carps and sediment with median diameter of 7 μm are tested, and sediment concentrations of 0, 200, 600, 800 and 1000 mg/L are used for each of the supersaturation levels of 125%, 130%, 135% and 140%. Results show that higher TDG supersaturation and sediment concentration leads to a shorter median lethal time of the rock carps exposed to the water. Sediment accelerates the death of rock carps in TDG supersaturated water, but supersaturated TDG plays the major role. We have observed that sediment alone did not result in the death of rock carps in all the treat groups (200-1000 mg/L) in the condition of TDG supersaturation level of 100%.