A fault isolation method, used in a Peripheral Component Interconnect Express, PCIe, interconnected computer system, wherein the computer system comprises a primary domain and an extended domain, the primary domain comprises a root complex, a first endpoint device, and a root complex endpoint device, and the extended domain comprises the root complex endpoint device and a second endpoint device, wherein the root complex endpoint device serves as the root complex in the extended domain; and the method comprises: monitoring a state of the second endpoint device in the extended domain; setting a device state record according to the state of the second endpoint device, wherein the device state record comprises a correspondence between identifier information of the second endpoint device and the state of the second endpoint device; receiving an access request, wherein the access request comprises an access request from the second endpoint device of the extended domain to the primary domain or an access request from the primary domain to the second endpoint device of the extended domain; querying the device state record according to the identifier information that is of the second endpoint device and in the access request, and determining the state of the second endpoint device; and discarding the access request to prevent communication between the second endpoint device of the extended domain and the primary domain when the state of the second endpoint device is a fault state; wherein the method further comprises: configuring a first memory address and a second memory address for the second endpoint device, the first memory address is used to represent the second endpoint device in the primary domain, the second memory address is used to represent the second endpoint device in the extended domain; configuring a bus/device/function, BDF, identifier for the second endpoint device; storing a mapping relationship between the BDF identifier of the second endpoint device and the second memory address of the second endpoint device; and storing a mapping relationship between the first memory address of the second endpoint device and the second memory address of the second endpoint device. monitoring a state of the second endpoint device in the extended domain; setting a device state record according to the state of the second endpoint device, wherein the device state record comprises a correspondence between identifier information of the second endpoint device and the state of the second endpoint device; receiving an access request, wherein the access request comprises an access request from the second endpoint device of the extended domain to the primary domain or an access request from the primary domain to the second endpoint device of the extended domain; querying the device state record according to the identifier information that is of the second endpoint device and in the access request, and determining the state of the second endpoint device; and discarding the access request to prevent communication between the second endpoint device of the extended domain and the primary domain when the state of the second endpoint device is a fault state; wherein the method further comprises: configuring a first memory address and a second memory address for the second endpoint device, the first memory address is used to represent the second endpoint device in the primary domain, the second memory address is used to represent the second endpoint device in the extended domain; configuring a bus/device/function, BDF, identifier for the second endpoint device; storing a mapping relationship between the BDF identifier of the second endpoint device and the second memory address of the second endpoint device; and storing a mapping relationship between the first memory address of the second endpoint device and the second memory address of the second endpoint device. configuring a first memory address and a second memory address for the second endpoint device, the first memory address is used to represent the second endpoint device in the primary domain, the second memory address is used to represent the second endpoint device in the extended domain; configuring a bus/device/function, BDF, identifier for the second endpoint device; storing a mapping relationship between the BDF identifier of the second endpoint device and the second memory address of the second endpoint device; and storing a mapping relationship between the first memory address of the second endpoint device and the second memory address of the second endpoint device.