The compound underflow stilling pool adapted to the needs of engineering terrain has been widely used in small and medium-sized reservoir projects because of its simple layout and low engineering cost, but it has various disadvantages such as complex flow pattern and low energy dissipation rate under asymmetric inflow conditions. Based on the flood discharge and energy dissipation structure in the lower reservoir of Funing Pumped Storage Power Station, the energy dissipation type and inflow mode of the compound stilling pool are studied by means of hydraulic model test and numerical simulation. The results show that when the conventional uniform and symmetric inflow mode is adjusted to an appropriate asymmetric one, the space range of inflow water in the stilling pool is expanded, the asymmetric inflow not only takes the advantage of high energy consumption rate of ternal hydraulic jump, but also eliminates the problem of flow rotation in the stilling pool caused by non-uniform inflow and asymmetric body type of the stilling pool. Experiment and numerical calculation results show that the underflow energy dissipation of this arrangement type greatly improves the shear collision between the incident water body and the downstream water cushion, reduces the underflow velocity and floor pressure, and keeps the flow state stable, it can increase the total energy consumption rate of the stilling pool by about 10%, and meets the requirement of safe operation under various working conditions in the same time.