Curing processes of hydroxyl-terminated polybutadiene(HTPB) with different molecular weight (M1:1500; M2:2800)/2, 4-toluene diisocyanate (TDI) systems were studied by rotational viscometer and non-isothermal differential scanning calorimetry(DSC), and effect of molecular weight on curing reation kinetic of system was investigated. Results show that the viscosity of M1 system increases faster than that of M2 system, and the curing reaction heat of M1 systems is greater than that of M2 system. The values of apparent activation energy, reaction order and pre-exponential factor of M1 system are 55.87 kJ·mol^-1, 0.88, 4.70×10⁴ s^-1, respectively. While for M2 system, the peak temperature of the curing process increases and the values of apparent activation energy, reaction order and pre-exponential factor increase to 60.77 kJ·mol^-1, 0.89, 1.07×10⁵ s^-1, respectively. The curing reaction mechanism of two curing system follows f(α)=(1-α)ⁿ and index n of M1 system curing reaction is only slightly different from that of M2 system.