Dynamic mechanical property of HTPB propellant after storage aging was investigated by using dynamic mechanics analysis method. The relational graph of time displacement with logarithm of frequency and the constant of WLF equation were obtained based on time-temperature superposition. Critical temperature tc of propellant in ignition instant for solid rocket propellant was also calculated. It was predicted that HTPB propellant would not change from high elasticity state to glass state and destroy structure integrity.