Abstract: The mechanical properties of steel will change after strain aging, which will affect the structural safety. However, there are few researches on the mechanical properties of high-strength steel after strain aging in the field of construction engineering. This paper takes Q690D high-strength steel as the research object to carry out a study on the influence of strain-aging on the basic mechanical properties of steel. Based on the test data, the basic mechanical indexes of Q690D steel after strain-aging are analyzed. The two-stage Ramberg-Osgood model is used to fit the test results, and an evaluation formula for the mechanical properties of steel after strain-aging is proposed. The constitutive relationship of Q690D steel under different strain aging conditions is predicted. The results show that after strain aging, the yield strength of Q690D steel significantly increases, the ductility decreases, and the strain hardening disappears completely after 4% pre-strain. The proposed mechanical properties evaluation formula can predict the mechanical properties under different pre-strains and different aging. The two-stage Ramberg-Osgood model can accurately characterize the stress-strain curves of Q690D steel under different pre-strains (2%~4%) and different aging (0 d~90 d). The research results can provide useful reference for the evaluation of mechanical properties and the recycling of high-strength steel after strain aging.