The invention discloses a flow adjustment energy dissipation device installed inside a container and used for a nuclear power plant. The flow adjustment energy dissipation device comprises a cylinder installed inside the container, a piston arranged in the cylinder, and a piston driving device used for driving the piston. A plurality of through holes are formed in the peripheral wall of the cylinder. The piston is driven by the piston driving device to move along the cylinder in the axial direction, so that the number of the through holes through which liquid passes is changed, the flow of the liquid is adjusted, and the flowing direction of the liquid is changed from the axial direction to the radial direction. Compared with the prior art, according to the flow adjustment energy dissipation device installed inside the container and used for the nuclear power plant, the multiple through holes are formed in the peripheral wall of the cylinder, so that the energy of the liquid entering the container is dissipated; in addition, by changing the number of the through holes through which the liquid passes, the liquid flow is adjusted through the axial movement of the piston; in this way, fluctuation, vortexes and turbulent flow generated by the liquid in the container can be effectively reduced, the stability of the liquid at an irrigating gate of a pump is guaranteed, and the vibration and noise generated by a circuit system are greatly reduced.