T-PNIMMO with three functional groups was synthesized by cationic ring opening polymerization of NIMMO (3-nitratomethyl-3-methyloxetane) in the presence of TMP (trimethylolpropane) catalyzed by BF₃·OEt₂. Then AUTPNIMMO was synthesized by T-PNIMMO and allyl isocyanate. The polymers were characterized by FTIR, ¹H NMR, 13C NMR, and their thermal stability was estimated by DSC. Moreover, tensile testing was used to evaluate the mechanical properties of polyurethane elastomer based on T-PNIMMO and toluene-2,4-diisocyanate (TDI), and isoxazoline elastomer based on AUT-PNIMMO and tetramethyl-terephthalobisnitrile oxide (TTNO). This showed an increase of tensile strength from 2.0 to 4.0 MPa and elongation at break from 150% to 500%, respectively. These results indicated that AUTPNIMMO exhibited a good thermal stability, had satisfactory mechanical properties and was expected to be used in the composite solid propellant and polymer bonded explosives.