A gas pipeline was reported to have a large number of pipe body crack defects after in-line inspection. For the quantitative analysis of the failure probability of pipe crack, this paper summarizes the structural integrity assessment method based on structural-reliability analysis. According to the British standard BS 7910:2013, certainty evaluation method and structural-reliability analysis evaluation method based on Monte Carlo simulation were carried out to evaluate the acceptability of the gas pipeline pipe body crack defects, and two kinds of evaluation methods were analyzed comparatively. The certainty evaluation results can only show whether the defects are acceptable or not and whether the partial factor is considered or not has great influence, and through the Matlab programming calculation, the pipeline failure probability is 3.17×10-3after the 107simulation using Monte Carlo. The structural integrity assessment method based on structural-reliability analysis can analyze the failure probability of oil & gas pipeline pipe body crack defects quantitatively. Compared with the certainty evaluation, the structural integrity assessment method based on structural-reliability analysis is more convenient for pipeline management departments to balance pipeline failure risk and maintenance cost, which is of great significance for guiding reasonable maintenance decision-making.