In view of the existing decoding scheme of poor portability and low efficiency, the article analyzes the basic concepts, functions and message structure of the Diameter protocol in LTE (Long Term Evolution) network, then puts forward innovative decoding solutions by using dictionary method to resolve Diameter protocol. After testing by the current network data, the scheme has been verified to be correct and feasible, and effectively solves the decoding issue of Diameter protocol different message types in the LTE network.