In order to deeply understand the curing reaction process of 3，3-bis（azidomethyl）oxetane/tetrahydrofuran copolymer （PBT） binder and polyisocyanate curing agent （N100）， the modulus changes during the entire isothermal curing process and the viscosity changes before gelation for PBT/N100 binder system was studied by using a rheometer. The results show that the entire isothermal curing process of PBT/N100 binder system follows the autocatalytic kinetic model. According to the change of modulus with curing time， the curing process of PBT/N100 binder system is divided into reaction-control stage， gelation stage and diffusion-control stage. Dual-Arrhenius model can be used to describe the changes of viscosity in the reaction- control stage. The activation energy for viscosity and the activation energy for reaction are 36.271 kJ/mol and 54.882 kJ/mol， respectively. The Eyring model is used to calculate the thermodynamic parameters ΔH and ΔS during the curing process， which are 52.07 kJ/mol and -125.55 J/（mol·K）， respectively. It is basically confirmed that the ideal isothermal curing temperature for PBT/N100 binder system is 60 ℃， and the curing time is about 160 h.