The influence of H2S interaction with prestrain on the mechanical properties of high-strength X80 steel was investigated by slow strain rate tensile tests and hydrogen content measurements. Results showed that elongation to failure first decreased and then increased with increasing prestrain. Moreover, hydrogen content decreased but the relative hydrogen embrittlement(HE) susceptibility, determined by measuring the relative reduction in failure time, increased as H2S introduction changed from the origin to the plastic stage. Fractography exhibited brittle fracture for H2S-introduced specimens and necking phenomenon decreased significantly compared with H2S-free specimens. Secondary cracks in the lateral fracture surface increased with increasing prestrain, indicating higher HE susceptibility. The observations were discussed on the basis of the hydrogen-enhanced decohesion mechanism, H2S interaction with prestrain was closely associated with mechanical property degradation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.