Abstract: In order to study the energy dissipation characteristic of two jet-flow with varying discharge ratio,the unsteady in compressible flowing N-S equation,RNG k-ε turbulence model and VOF(volume of fluid)method are adopted to do the numerical simulation with reference to the Xiluodu double curvature arch dam. The impact pressure on the bottom slab of the plunge pool,the velocity and the fluid state characteristic of different flow ratio are analyzed,and the mean dynamic variation regulation in the field of flow is studied quantitatively. The research shows that,with the decreasing of the upstream jet-flow, the impact pressure on the bottom slab also decreases,and the flowing water cushion exerted by the upstream flow also lowers which makes impact pressure of the downstream flow increase gradually. There are two statuses of the plunge pool:one is the flow with the effect of flowing water cushion,the other is the flow with weakened flowing water cushion. The quantitative calculation shows that for the upstream jet-flow,the mean velocity gradient is larger,and the mean dynamic attenuation is quicker With the jet-flow lessening,the mean dynamic attenuation becomes faster than before. The discharge and dissipation ratio of the downstream are totally smaller than those of the upstream. The article gives a good reference for optimization design,the protection of plunge pool and the multi-jetting flow ratio determination.