To gain a foam plastic with excellent mechanical properties, tensile mechanical properties of methacylic acid/acrylonitrile (MAA/AN) copolymer and the corresponding foam microstructure were studied, and furthermore effects of the density, heat treatment, and crosslinking agent on foam mechanical properties were also discussed in this paper. The results reveal that the tensile strength and modulus of the copolymer after heat treatment are 64 MPa and 4.2 GPa respectively, when compared with 58 MPa and 3.8 GPa before heat treatment respectively. Foam mechanical properties are enhanced with the rise of the density, and the values tested accords with the theoretical values of pentagonal dodecahedron mechanical model basically. Foam mechanical properties are enhanced via heat treatment, and the same result can be observed after using the crosslinking agent (acrylamide) too. All these results indicate that MAA/AN copolymer foam possesses excellent mechanical properties, such as its tensile, 10% compressive and shear strength are 1.3, 0.8, and 0.8 MPa respectively when the foam density is 52 kg/m(3).