An integrated system of circuits for serial fan structure includes a first and a second fan connected back to back. A first driving unit and a first control unit for the first fan and a second driving unit and a second control unit for the second fan are sequentially electrically connected to a circuit board in the second fan. Further, a first coil assembly of the first fan and a second coil assemble of the second fan are also electrically connected to the circuit board in the second fan; and some low-use-rate electronic circuits are included in a common circuit unit of the first and the second fan. Therefore, the serial fan structure can save one circuit board and some low-use-rate electronic circuits from the first fan to achieve the purpose of reducing the manufacturing cost of the serial fan structure.