Objective To study the stress corrosion cracking (SCC) behavior and mechanism of X80 pipeline steel in the simulated trapped solution of Yingtan-soil in China under disbonded coating. Methods The potentiodynamic polarization, slow strain rate test (SSRT) and corrosion morphologies examination by scanning electronic microscopy (SEM) were applied for the research. Results X80 pipeline steel had high SCC sensitivity in simulated trapped solution, and the corrosion type was TGSCC. The SCC susceptibility of X80 pipeline steel in trapped solution of near-breakage region, lower parts and bottom was higher than others. The mechanism in trapped solution of near-breakage region was controlled by anodic dissolution (AD). And in trapped solution of bottom, the mechanism of X80 pipeline steel was mix-controlled by anodic dissolution and hydrogen embrittlement (AD+HE). Conclusion When a coating of X80 pipeline steel used in acid soil environment was disbonded, in addition to corrosion at the open breakage, stress corrosion cracking also occurred under the disbonded coating.