A protecting circuit for a basic input output system (BIOS) chip of a computer includes a platform controller hub (PCH), an inverting circuit connected to the PCH, a BIOS socket to connect the BIOS chip, and a controlling circuit connected between the inverting circuit and the BIOS socket. The PCH outputs a first signal or a second signal, and a third signal. The inverting circuit outputs an inverted signal with a level contrary to the first or second signal. The controlling circuit receives the first or second signal and the inverted signal, to output a processing signal to the BIOS socket, thereby controlling write-protection states of the BIOS chip.