Expansion joint from a bellows and the two posed to take over. It bellows through the flexible deformation to absorb the pipeline axial displacement (a small horizontal, angular displacement), or directly take over the terminal and pipeline to take over welding, or welding on the flange connection with the pipeline flanges. Expansion joint on the tension bar on the main transport is in the process of rigid support or as the product with pre-deformation adjustment, it is not bearing pieces. Such expansion joint structure is simple, low prices