Embodiments of this application disclose a remote attestation mode negotiation method for a combined device and a related device. The combined device may include at least a first unit. The method implemented by the first unit includes: sending a mode negotiation request message to the remote attestation device; receiving a mode negotiation response message comprising a target remote attestation mode; and determining the remote attestation mode based on the mode negotiation response message. In this way, a target remote attestation manner to be used subsequently can be determined through negotiation between the combined device and the remote attestation device, to provide a data basis for subsequently and sequentially performing remote attestation on the combined device.