Nano indentation and splitting test were used to study the nano indentation elastic modulus, nano indentation hardness, interface bond splitting tensile strength, cement paste tensile strength and compressive strength and correlation of coral aggregate and cement paste interface specimens at different ages. The results show that similar to ordinary concrete, coral concrete has a weak interface transition zone(ITZ). Adding 10% coral micro powder can strengthen the macro and nano mechanical properties of ITZ. The interface bond splitting tensile strength is not only linearly related to the compressive strength or splitting tensile strength of the cement paste matrix, but also to nanometer mechanical properties of interface transition zone and cement paste matrix.