Abstract: Based on the design of thorium-based ADS fast-thermal coupled subcritical reactor, the burnup characteristics during the lifetime with constant power were calculated using the Monte Carlo code MCNTRANS. Transmutation ability, plutonium brunup performance, k_eff change during the lifetime and the coordination of accelerator beam current were analyzed. The results indicate that the MA transmutation support ratio of the designed core is 15 PWRs of million kilowatt and the long life fission product (LLFP) transmutation support ratio is 2.2 PWRs of million kilowatt. In addition, the fission contribution of ²³³U in the thermal zone is 25% so that the ability of transmutation and proliferation of the core is strong. Besides, the change of k_eff in the lifetime is about 1% which can reduce the requirements of the accelerator beam intensity.