Using hydroxylated carbon nanotubes (CNT-OH) as a crosslinking agent, covalently modified CNT/3,3′-bisazidomethyloxetane-3-azidomethyl-3′-methyloxetane (BAMO-AMMO) thermoset polyurethane elastomers with different CNT-OH content were prepared, and their structure and performance were analyzed. At a CNT-OH mass fraction of 1.0 wt%, the elongation ratio was 380% and the tensile strength was measured to be as high as 10.4 MPa, which is an 82.5% improvement compared to traditional trimethylolethane (TME)/BAMO-AMMO energetic binders. The measured onset decomposition temperature (i.e., the temperature with 5% weight loss) was 236°C, which is 7°C higher than that of corresponding TME/BAMO-AMMO energetic binders. Furthermore, the identified glass transition temperature (Tg) was −34°C.