A method, system and device for device capabilities exchange are provided. The method for device capabilities exchange includes: receiving a device capability exchange request sent from an initiating Diameter node; and returning a device capability exchange answer to the initiating Diameter node according to a state of a state machine of a receiving Diameter node or a request type in the device capability exchange request. The method can optimize the existing method for updating and negotiating device capability information when a Diameter device is upgraded, reduce the amount of data exchanged over the network, reduce the repetition of database update performed by the Diameter nodes, and improve the robustness of network connection and system processing.