<p>Excellent mechanical advantages of high-strength structural steel (HSS) facilitate its application in complex conditions instead of ordinary structural steel, but its stress–strain behavior under the combined effect of multiple factors still needs to be investigated. This paper investigates the tensile stress–strain behavior of HSS after different levels of pre-damage (0, 2, 4, 6%) and high-temperature exposure (200, 400, 600&#xa0;°C). The effects of welding on the tensile strength of HSS are also studied by preparing two types of specimens, with and without welds. The obtained results show that the plastic deformation capacity of the specimens significantly decreases with the fracture strain (ε_<i>f</i>) due to the pre-damage. However, both the tensile strength and yield strength of the specimens without and with welds at 15&#xa0;°C increased with the degree of pre-damage. Moreover, strain aging effect becomes more pronounced as the increase in pre-damage level. Based on the experimental results, the strain energy density (SED) and fracture energy density (U) under the combined action of pre-damage and high temperature were calculated.</p>