Abstract: Properties of coarse aggregate, interface and mortar are main factors in the tensile constitutive relation of concrete. The surface of recycled coarse aggregate is usually covered by an old mortar layer, making it much different in properties from natural aggregate. The paper describes a five phase meso-scale numerical model of recycled coarse aggregate concrete (RCAC) that is based on the random aggregate model, and verifies its reliability using our test results. For this concrete, we also examine the trend in damage development and the effect of strength and thickness of the old mortar layer on its tensile properties, and construct its tensile constitutive relation based on our analytical results. The results show that the tensile damage to RCAC under uniaxial tension loads starts at the transition zone on an aggregate-mortar interface and then expands to the old and new mortar layers until cutting through the section of structure. When the old mortar layer is thin or its strength is greater than that of new mortar, RCAC has little change in tensile properties as the thickness or strength of old mortar layer is varied. Otherwise, its tensile stress, elastic modulus, and peak deformation modulus are all increased with an increase in the strength or a decrease in the thickness of old mortar layer. And the peak tensile strain of RCAC increase proportionally with the strength and thickness of old mortar layer.