During the gas transmission pipelines survice, the change of gas transmission volume will result in pipeline burden pressure fluctuation, which will suffer fatigue damage of the pipeline, and thus a threat to pipeline safety. Therefore, in this paper, the mechanical properties of girth weld no welding defect and containing welding defects were investigated, and the safety probability and confidence level of pipeline with no girth welding defect and containing welding defects are normally considered. The stress spectrum of the pipeline is established according to the fatigue P-S-N curve of the girth weld and the nonuniform coefficient of the gas flow in the pipeline. On this basis, the fatigue reliability life of welded joints of high-pressure gas pipeline is evaluated by the principle of damage accumulation. It is shown that the service life of high strength pipeline with typical girth welding defects is more than 30 years. This method can provide the basis for the fatigue life analysis and reliability evaluation of the pipeline, and has certain engineering application value.