The invention discloses a high-temperature pipeline combining and fixing device. Structurally, a floating structure which is arranged outside a pipeline in a sleeving manner is mounted at a part to be fixed, of the pipeline; a baffle plate which is fixed on the outer wall of the pipeline is arranged on a bearing side of the floating structure; one side of the floating structure is connected with a support frame arranged on two sides of the pipeline through pull rod components; linear displacement constraint along the pipeline in the axis direction is achieved through the pull rod combined structure, and the axial force of the pipeline can be born. In addition, a guide bracket is mounted at the bottom of the pipeline, and radial rotation of the pipeline is limited by the anti-rotating baffle plate on a guide support base below the guide bracket. The purpose of fixing the pipeline is achieved, and meanwhile thermal expansion of the high-temperature pipeline is not constrained, so that the stress level of a connecting part can be greatly reduced, the probability that attachment weld and process pipelines are cracked in long-term high-temperature operation is effectively avoided, and the requirements of full-load long-term security operation of process pipelines of high-temperature large-aperture petrochemical plants can be completely met.