Abstract: Aiming at the common engineering problems of low discharge efficiency in the initial stage and large outburst flood peak of high-risk barrier lakes, we respectively adjust the lateral and longitudinal spillway structure through an indoor physical model and then comparatively investigate the outburst flood differences between the conventional trapezoidal, compound and the vertical scarp spillways.The results show that the outburst flood process can be successively divided into four feature stages, namely the initial stage, backward-source stage, swift development stage and the recovery stage.Compared to the conventional spillway, the compound spillway can effectively reduce the overflowing elevation of barrier body, accelerate the development of initial stage, and shorten water storage time of the barrier lake, thus lowering the water level of the lake and shaving the outburst flood peak by 17%.The vertical scarp spillway would significantly increase the local velocity to accelerate backward-source scouring, accelerate the development of initial stage, and shorten water storage time of the barrier lake, thus lowering the water level of the lake and shaving the outburst flood peak still by 11.4%.