Abstract: The solid tritium breeder test blanket module (TBM) can constantly provide tritium for D-T reaction in the fusion reactor, and it is the key to realize fusion in business application. As the ratio of area to volume is large and the production efficiency of tritium is high, the development of the module made with ceramic lithium pebble beds is focused in China. The tritium breeder pebble bed should sustain the high temperature environment in the reactor, and this requires the pebble bed must have excellent thermal conductivity. The effective thermal conductivity of the pebble bed is important in the design phase and safety analysis phase of TBM. The irradiation experiment was carried out in China Advanced Research Reactor (CARR) to aim at measuring the effective thermal conductivity of the tritium breeder pebble bed. The effective thermal conductivity of the pebble bed was calculated with the heat generation power obtained with MCNP and the temperature distribution in the irrational experiment. The results of the calculation are shown to be in good agreement with the results obtained in the out of pile measurement experiment and theoretical results of the modified ZBS model.