The invention relates to a finite element analysis based pipeline random vibration fatigue life analyzing method, which mainly includes: by finite element analysis, after acquiring response of structural dynamic stress power spectrum density (PSD) on the condition of random vibration of pipelines, combining a damage model and a material S-N curve (stress-number of cycles curve) to compute fatigue life of a pipeline structure, and accordingly, judging whether the pipeline structure stays at the safety working state or not, if not, optimizing the pipeline structure until the pipeline structure is qualified. The finite element analysis based pipeline random-vibration fatigue life analyzing method solves the problem about vibration fatigue life analysis prediction of existing launcher model pipelines and provides guidance and verification for design and test of pipeline vibration fatigue life, can effectively analyze and predict the fatigue lives of the liquid launcher pipelines under the action of random-vibration load, provides guidance and verification for fatigue design of the pipeline structures, is sufficiently applied in the computing analysis of conveying pipes of manned space launchers and achieves excellent effect.