Polyurethanes were initially synthesized with MDI, polyester type polyol and chain extender containing conjugated diacetylene groups. Interchain cross-linking reaction between diacetylene groups was achieved by UV-irradiation or heat treatment. Interchain cross-linking reaction between diacetylene groups was confirmed with the Raman spectroscopy and the extent of crosslinking reaction was observed by increasing the UV irradiation time or heat treatment time. Cross-linked polyurethanes exhibited higher stress than linear polyurethane at the same strain level. The chemical cross-linkages between diacetylene groups appeared to make more stable hard domain to the external deformation.