This study aimed to investigate the macroscopic performance degradation and microstructural evolution of polyurethane (PU) coatings for double-base propellants after long-term storage, and to elucidate their warming-accelerated aging mechanism. Taking polyether PU coatings as subject, infrared spectroscopy, thermogravimetric analysis, mechanical testing, gas chromatography-mass spectrometry and low-field nuclear magnetic resonance were employed to analyze the changes in properties and structure after 10 years of storage with the propellant charge. The experimental results demonstrate a notable decline in tensile strength from 5.06 MPa to 3.53 MPa, representing a reduction of 30% . Concomitantly, the Shore A hardness drops from approximately 76 to 66. And the temperature corresponding to 5% mass loss and the maximum mass loss rate are advanced by more than 70 ℃ . The microstructural analysis reveals that the elevated temperature significantly accelerates the decrease in the crosslink density of PU. The aging degradation is primarily attributed to the oxidative chain scission of polyether segments catalyzed by nitrogen oxides released from nitrate ester decomposition, as well as the thermal decomposition of carbamate bonds.