A circuit board assembly, a backplane interconnection system, and an electronic device are disclosed. The circuit board assembly includes a bracket and a circuit board, the circuit board is formed with a fastened part and a free part, the fastened part is connected to the bracket, the free part is suspended, a surface on which the free part and the fastened part are co-located is a first plane, the free part has an amplitude of swing in a first direction, the first direction is perpendicular to the first plane, the circuit board is configured to plug-connect to a front sub-circuit board, a first connector plug-connected to a first plug-connection end on the front sub-circuit board is disposed on the free part, and the amplitude of swing is capable of enabling the first connector to plug-connect to the first plug-connection end.