The curing reaction kinetics of dimeryl diisocyanate (DDI) / hydroxyl-terminated polybutadiene (HTPB) system was studied using Fourier transform infrared (FT-IR)spectra and compared with that of isophorone diisocyanate (IPDI)/HTPB system. The application of DDI in HTPB propellant was preliminary explored. Results show that the curing reaction of DDI/HTPB system appears as the second-order reaction and the apparent activation energy is 37.02 kJ·mol^-1, which decreases by 3.5 kJ·mol^-1 compared with that of IPDI/HTPB system, revealing that the reactivity of DDI is slightly higher than that of IPDI. And DDI has a moderate reactivity, which can be used as low-toxic curing agent in HTPB propellant. The DDI/HTPB system possesses better mechanical properties at room temperature with the tensile strength of 0.85 MPa, and the strain at maximum load of 44.1%. The room temperature mechanical property of DDI/HTPB system can meet the requirements of mechanical properties at room temperature basically for propellant.