Abstract: Experimental study of the full curve of the stress-strain relationship for microconcrete and concrete was conducted using a special stiffness instrument. A series of the full curve of the stress-strain for microconcrete and concrete was obtained. The mechanical properties are analyzed in this paper. These mechanical properties include stress-strain curve, compressive strength, peak stress and its corresponding strain, initial modulus of elasticity of microconcrete and concrete. The results showed that the mechanical properties of microconcrete are similar to the mechanical properties of concrete, and microconcrete can be used in the model tests of reinforced concrete, although microconcrete and concrete have some different mechanical properties. The validity of the stiffness instrument is verified for obtaining the full curve of the stress-strain of microconcrete and concrete simultaneously.