Abstract: It is necessary to build in-pipe tritium breeder in our country in order to assess breeder material of tritium breeder module (TBM) and to find the release law of tritium. The irradiation vessel is one of the key components of TBM. The physical parameters about in-pipe tritium breeder were simulated with MCNP code. The values of the self-shielding factor, equivalent cross-section, daily production of tritium and total heating power are separately 0.435, 1.09×10^-22 cm², 2.8×10¹⁰ Bq and 8.2 kW. And they would provide necessary data for designing the irradiation vessel.