Abstract: Three kinds of PU/PMMA i.e., Linear polymer, block copolymer and interpenetrating polymer network (IPN), were synthesized by the simultaneous polymerization process respectively. The effects of factor such as photo-setting, heat-setting, chemical composition and physical structure on morphological structure and mechanical properties of polymers were studied with scanning electron microscopy, dynamic mechanical loss spectrum and mechanical tests. The results are as follows: PU/PMMA is a partly compatible system with two phase structure. Among them, the linear polymer has the highest elongation at break, IPN shows the strongest tensile strength while the block copolymer has poor mechanical properties. In addition, photo-set block copolymer and IPN system, with regular microphase domain structure, have higher tensile strength and elongation at break than those of heat-set polymers. As the contents of PMMA and hard segment in PU increase in the system, the tensile strength increases while the elongation at break descends.