Abstract: In order to study the stability and stress-strain relationship of steel slag coarse aggregate concrete, the water immersion expansion rate and autoclaved pulverization rate of steel slag coarse aggregate of a steel company in Baotou were experimentally determined and the content of free CaO was tested. Six groups of cubic compression tests and prismatic uniaxial compression tests under different slag replacement rates were completed to analyze their failure modes and deformation characteristics, and establish the constitutive model of steel slag coarse aggregate concrete. The results show that the free CaO content, the water immersion expansion rate and the autoclaved pulverization rate of steel slag used in the test meet the requirements of relevant specifications with excellent stability. The uniaxial compressive strength of steel slag coarse aggregate concrete rises with the increase of steel slag content, and is higher than that of ordinary concrete, presenting more obvious failure brittleness. The ratio of prism compressive strength to cube compressive strength of steel slag coarse aggregate concrete is also higher than that of ordinary concrete. According to the constitutive model by Guo Zhenhai and the Wee model, the constitutive relationship of steel slag coarse concrete can be described in sections with consideration of the correction coefficient of steel slag coarse aggregate content. The stress-strain model is in good agreement with the test results and can be used to describe the mechanical behavior of steel slag coarse aggregate concrete under uniaxial compression more comprehensively.