The invention relates to a monitoring and early-warning device for a sleeve expansion joint and a monitoring method thereof, and belongs to the technical field of intelligent monitoring. The monitoring and early-warning device is characterized in that a camera is arranged on a fixing end pipe, and holes are formed in the fixing end tube for installing a pressure sensor and a temperature sensor; abracket is arranged on a movable core pipe and an outer cover, and an axial displacement sensor is arranged on the bracket; a wire is laid on the inner surface of the outer cover, and one end of the wire is connected with a leakage alarm sensor; and the axial displacement sensor is connected with an analog quantity acquisition module, the leakage alarm sensor is connected with the analog quantityacquisition module, the pressure sensor is connected with the analog quantity acquisition module, the temperature sensor is connected with the analog quantity acquisition module, and the camera is connected with a wireless router. The monitoring and early-warning device has the advantages and beneficial effects that sleeve expansion joint can be comprehensively monitored, whether the sleeve expansion joint needs to be replaced or not can be pre-judged, or whether the sleeve expansion joint can keep running to the maintenance period or not can be pre-judged according to the damage degree of thesleeve expansion joint, and therefore the problem that the sleeve expansion joint is suddenly damaged in the operation process of a pipe network is fundamentally solved, the phenomenon that the pipenetwork suddenly stops running due to the fact that the sleeve expansion joint is damaged is avoided, and loss caused by shutdown is reduced; and moreover, installation is convenient, and energy is saved.