A computer system and a method are provided for accessing a peripheral component interconnect express (PCIe) endpoint device. The computer system includes: a processor, a PCIe bus, and an access proxy. The access proxy connects to the processor and the PCIe endpoint device; the processor acquires an operation instruction, where the operation instruction instructs the processor to access the PCIe endpoint device through the access proxy, and send an access request to the access proxy according to the operation instruction; and the access proxy sends a response message of the access request to the processor after receiving the access request sent by the processor. Because the processor does not directly access the PCIe endpoint device to be accessed but completes access through the access proxy, thereby avoiding an MCE reset for the processor.