The invention discloses a process for mounting a relatively long pipeline. The process comprises the following steps of: 1, determining the spreading length of the pipeline; 2, designing a supporting rod; 3, spreading the pipeline, mounting accessories on the pipeline, conveying the spread pipeline and the supporting rod to an assembly place, putting the pipeline in a set range of a module, and putting a hoister in place; 4, connecting a hook of the hoister and a chain block and a steel wire rope, and connecting the steel wire rope and a hoisting point of the supporting rod and then the supporting rod; 5, hoisting the pipeline in trial, and then formally hoisting the pipeline after determining that the deformation and the intensity of the pipeline meet the requirements; and 6, mounting the pipeline in place, detaching the hoisting rope after the pipeline is mounted in place, and resetting the hoister. According to the process, pipelines which are in different types, made of different materials and relatively long can be installed; furthermore, the working amount of welding the pipeline on the spot is reduced, damage to a pipeline base material is prevented, and the working efficiency is improved; and furthermore, the influence of a plurality of hoisters on the deformation of the pipeline is reduced.