The invention relates to a sealing structure and a sealing method used for the pipeline of a press filter, comprising a pipeline and a frame; one end of the pipeline is provided with a flange; the pipeline passes through the frame and form a clearance fit with a transition plate; the pipe wall at the other end of the pipeline is opened with a ring-shaped concave trough; a ring-shaped sealing ringis arranged in the ring-shaped concave trough and hermetically matched with the transitional plate. The sealing structure and the sealing method have the advantages that: with ensuring the reliable sealing of the external diameter of the pipeline and the aperture of the pipeline of the transition plate, the deformation or cracking problem caused by hot-expansion and cold-contracting effect of thepipeline in the prior art is solved, and the technical difficulty problem which people want to solve but do not solve is solved.