Abstract: A method for supporting USB input devices via BIOS, which allows BIOS to support USB input devices when the motherboard does not have the keyboard controller (KBC). This method is especially applied to the operating systems that do not support the drivers for USB keyboard and mouse input devices, and BIOS can still support existing USB keyboard and mouse input devices. It is implemented by connecting two general purpose output pins of a south bridge (SB) on the hardware to an 8259 programmable interrupt controller (PIC) chip on the SB and revising some part of the internal program in BIOS to simulate and create hardware interruption requests IRQ1 and IRQ12. This can achieve the object of backward compatibility. and support usual chipsets on the market by merely revising the firmware.