The switching circuit

The invention discloses a switching circuit, which comprises a first connector, a first platform controller hub (PCH), a first basic input output system (BIOS), a diagnosis card and a switch circuit. The PCH comprises a first strapping pin and a second strapping pin. The diagnosis card comprises a second connector and a second BIOS. The second connector is plugged into the first connector. The second BIOS is used for outputting a high-potential control signal. The switch circuit is used for receiving the control signal sent from the second BIOS. When the switch circuit receives the high-potential control signal, the switch circuit outputs a high-potential switch signal to the first and second strapping pins of the PCH. When the switch circuit does not receive the high-potential control signal, the switch circuit outputs a low-potential switch signal to the first and second strapping pins. The switching circuit can be used for conveniently switching the first or second BIOS to start a main board, thereby bringing convenience to research personnel.