The invention relates to the field of plastic pipelines or plastic composite pipeline welding and aims to provide a pipeline electric fusing joint adopting a tenon-and-mortise structure and an electric fusing welding method. The pipeline electric fusing joint comprises two opposite pipeline end heads respectively connected to two sections of pipes; the end surface of one pipeline end head is provided with an annular protruded part, while the end surface of the other pipeline end head is provided with an annular groove; the protruded part is matched with the size and the shape of the groove; and when the protruded part enters the groove, the two end surfaces are tightly adhered. The welding method is mainly characterized in that a resistance wire is embedded in a middle cold welding area of an electric fusing sleeve. In the invention, through using a plastic pipe or a composite pipe manufactured by using the pipeline electric fusing joint and the welding method, the interior of the electric fusing joint does not have a non-fused area, and compared with a traditional electric fusing joint, the pipeline electric fusing joint has better structural continuity and better mechanical property; and the condition that stress concentration is generated due to the existence of the cold welding area in the sleeve under the action of internal pressure, which causes that a crack runs throughthe sleeve, and the sleeve loses efficacy, can be avoided.