A new concept of tritium breeding blankets is introduced for fusion reactor systems using a 3He gas loop combined with neutron multipliers and moderators. To verify the tritium breeding capability of this 3He based blanket, several neutronic calculations have been made in one-dimensional cylindrical geometry and compared with those for the current Li based blankets. The results show that the tritium breeding ratio of the 3He gas loop blanket can exceed unity with a reasonable blanket thickness. In particular, the possibility of a “thin” tritium breeding blanket is suggested in a homogenized system of Be and 3He.With these neutronic survey calculations, the T-3He fuel cycle has been modelled to estimate the required amounts of tritium and 3He supplies. The feasibility of the 3He gas loop blanket system is discussed through considerations on the merits of this T-3He fuel cycle.