A power supply system for shelving system, comprising: a support arm, the support arm comprising a mounting hole, and a mounting plate disposed in the mounting hole, the thickness of the mounting plate being less than the depth of the mounting hole; and an electrical supply device, the electrical supply device being mounted on the mounting plate and comprising a circuit board, and a first protection cover covering the circuit board, the circuit board being clamping between the mounting plate and the first protection cover, a side wall of the first protection cover opposite to the circuit board being flush with a side wall of the mounting hole, wherein - the sum of a thickness of the circuit board and a thickness of the first protection cover is equal to the difference between the depth of the mounting hole and the thickness of the mounting hole; and/or - one side of the mounting plate is flush with that of the mounting hole, the circuit board is mounted in a groove form by the mounting hole and the mounting plate; and/or - the first protection cover is fixed on the mounting plate by fasteners; and/or - the electrical supply device further comprises a second protection cover, the second protection cover is disposed at one side of the circuit board opposite to the first protection cover, the circuit board and the mounting plate are clamped between the first and second protection covers (324, 325); and/or - at least two hollow holes are provided between the mounting plate and the mounting hole. a support arm, the support arm comprising a mounting hole, and a mounting plate disposed in the mounting hole, the thickness of the mounting plate being less than the depth of the mounting hole; and an electrical supply device, the electrical supply device being mounted on the mounting plate and comprising a circuit board, and a first protection cover covering the circuit board, the circuit board being clamping between the mounting plate and the first protection cover, a side wall of the first protection cover opposite to the circuit board being flush with a side wall of the mounting hole, wherein - the sum of a thickness of the circuit board and a thickness of the first protection cover is equal to the difference between the depth of the mounting hole and the thickness of the mounting hole; and/or - one side of the mounting plate is flush with that of the mounting hole, the circuit board is mounted in a groove form by the mounting hole and the mounting plate; and/or - the first protection cover is fixed on the mounting plate by fasteners; and/or - the electrical supply device further comprises a second protection cover, the second protection cover is disposed at one side of the circuit board opposite to the first protection cover, the circuit board and the mounting plate are clamped between the first and second protection covers (324, 325); and/or - at least two hollow holes are provided between the mounting plate and the mounting hole. - the sum of a thickness of the circuit board and a thickness of the first protection cover is equal to the difference between the depth of the mounting hole and the thickness of the mounting hole; and/or - one side of the mounting plate is flush with that of the mounting hole, the circuit board is mounted in a groove form by the mounting hole and the mounting plate; and/or - the first protection cover is fixed on the mounting plate by fasteners; and/or - the electrical supply device further comprises a second protection cover, the second protection cover is disposed at one side of the circuit board opposite to the first protection cover, the circuit board and the mounting plate are clamped between the first and second protection covers (324, 325); and/or - at least two hollow holes are provided between the mounting plate and the mounting hole.