© 2018 by the authors. SF/polyurethane composite non-woven sheet was fabricated to evaluate the cardiovascular tissue engineering materials in the wet state. The compatibility and microstructure analyses were carried out on the fabricated SF/polyurethane composite non-woven sheet by thermal analysis and solid-state NMR analysis in the wet state. To evaluate the modulus of elasticity, a tensile test was performed and supported with dynamic viscoelasticity and mechanical analysis. Results showed that SF/polyurethane composites form domains within the non-woven sheet and are in a finely dispersed state while maintaining their structures at a scale of several tens of nm. Moreover, an increase of the loss tangent with low elastic modulus proved that a micromolecular interaction occurs between silk fibroin (SF) and polyurethane molecules.