The present disclosure provides a method for outputting power-on self test information, a virtual machine manager, and a processor. The method includes: receiving trigger information generated by a BIOS program when the BIOS program runs a predefined virtual mode trigger instruction, starting, by a virtual machine manager, the virtual machine manager and monitoring a processor, where the processor is a processor that enters a virtual mode after receiving the trigger information of the BIOS program; when detecting that the processor generates an exit instruction, obtaining power-on self test information after the BIOS program performs a power-on self test operation, and outputting the power-on self test information to a serial port. Power-on self test information may be output without using a motherboard diagnostic card, so that device resources are saved. In addition, the operation is simple, and no human control operation is required.