Modified hydroxyl-terminated polybutadiene (HTPB)-based polyurethanes (PUs) were prepared by three different processes: crosslinkage of the soft segment, complexation of the hard segment, and the interpenetrating network (IPN). Crosslinked PU films were prepared by the addition of a crosslinking agent of divinylbenzene (DVB) to the 4,4 -dicyclohexylmethane diisocyanate (H 12 MDI) and 1,4-butanediol (1,4-BD)-based PUs. The ionic polymer was prepared by adding N-methyldiethanolamine (MDEA), which possesses tertiary amine used as chain extender, to the HTPB-H 12 MDI-based PUs and then complexed by cupric chloride with MDEA. An IPN was formed by the introduction of 4-vinylpyridine (4-VP) to the benzoyl peroxide (BPO)-crosslinked HTPB-H 12 MDI-1,4BD-based PUs. FTIR was utilized to identify the segregation between hard and soft segments and structure change, which affects the tensile properties. The change of the glass transition temperature was detected by DSC, which can be used to manifest the modified PUs. Thermal decomposition behaviors conducted by TGA were used to investigate the formation of an IPN. The hydrogen-bonding index (HBI), frequency difference, and shift as a measure of the phase segregation and the average strength of the interpolymer hydrogen bonds were utilized to study the intermolecular interaction and tensile property of the prepared PUs. The effect of the hard-segment content, DVB content, amount of cupric ion, and 4-VP content on the tensile property were investigated. The stress was largely increased by the modification of PUs, while the strain still remains an appreciable value compared with that of unmodified PUs.