A container energy storage system is provided, including a container, a plurality of functional assemblies, and a splitting plate, wherein the splitting plate has a connecting port electrically connected to the functional assemblies. The container includes a hollow main body having an opening and two doors pivotally connected to the hollow main body. The functional assemblies are disposed in the hollow main body, and the splitting plate is disposed between the functional assemblies and the opening. When the doors are in a closed position, the doors cover the opening.