The invention discloses a method, a device and a system for transferring Diameter messages. The method comprises the steps of receiving a position updating request from an MME by an HSS and obtaining a plurality of pieces of user signed data needing to be transmitted, when the length of a first position updating response carrying theplurality of pieces of user signed data does not exceed a preset message length threshold, transmitting the first position updating response to the MME, and when the length of the first position updating response exceeds the message length threshold, transmitting a second position updating response and at least one user data request to the MME, wherein the second position updating response and each user data request, and the user signed data carrying in the response and the request all can be processed by the MME independently, and the second position updating response and each inserted user data request both carry route marks. In this way, the segmentation and the recombination of messages at the bottom layer during the user position updating in the presence of lots of signed data are avoided, the transfer efficiency of the messages is improved and the transfer time delay is reduced.