Tensile properties and fracture behavior of X80 pipeline steel exposed to corrosion environments with different H2S/CO2 partial pressure ratios were investigated through slow strain rate tests (SSRT). The results show that the tensile properties of X80 steel were damaged in H2S/CO2 environments. The tensile strength and elongation to failure of X80 steel decreased significantly with increasing H2S/CO2 partial pressure ratio. The fracture appearance of the corroded samples exhibited mixed ductile brittle rupture. Fractured areas with quasi-cleavage features increased as H2S/CO2 partial pressure ratio increased. Different types of secondary cracks can be identified on the SSRT specimens in the corrosion environments with different H2S/CO2 partial pressure ratios. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.