Abstract: Physical and thermal calculation and analysis of irradiation in reactor of tritium breeder pebble bed assembly were carried out to verify the feasibility and security of the irradiation experiment of International Thermonuclear Fusion Experiment Reactor (ITER) tritium breeder blanket module (TBM) which will be carried out in China Advanced Research Reactor (CARR). The TBM is mainly aimed at solid tritium breeder ceramic pebble bed assembly (breeder material is Li₄SiO₄). The Monte Carlo particle transport simulation code to modeling the pebble bed was adopted in this paper. By using the statistical pebble bed neutron flux, counting card energy deposition and yield, the neutron flux rate, heating power and the rate of tritium production for the pebble bed under different powers were gotten, and the reactivity of pebble bed was introduced into reactor. In order to ensure the safety of the reactor and ceramic pebble bed assembly, one-dimensional thermal calculation model was established based on the heating power calculated by the physical simulation to meet requirements of the experiment. It can be realized by changing the structure size of pebble bed or the power of reactor. Three-dimensional thermal simulation code was used to ensure the safety of the pebble bed assembly. The physical and thermal calculation and analysis results show that the temperature of different parts of the pebble bed assembly will not exceed the limits when the reactor runs under 20 MW.