Abstract: An IPN from polyurethane of hydroxy terminated poly (butadiene-acrylonitrile)(HTBN) prepolymer and poly(methyl acrylate) was synthesized by simultaneous crosslinking polymerization. The relationship between the mechanical properties of IPNs and the ratio of components and NCO contents in polyursthane networks has been studied through the measurement of tensile strength, shear strength and TG analyses. The results showed that the IPN has better mechanical and thermal properties than the homopolymers from corresponding monomers. When PU/PMA=8/2, the mechanical property of IPNs showed a maximum value due to the synergy effect.