Attaining tritium self-sufficiency is indispens-able in a Z-pinch-driven fusion-fission hybrid reactor(Z-FFR).In this paper,a conceptual design is presented in which the Z-FFR tritium cycle system was divided into eight subsystems.A theoretical analysis of tritium inven-tory based on the mean residence time was performed to quantitatively obtain the tritium distribution in each sub-system.Tritium self-sufficiency judgment criteria were established using a tritium mass flow analysis method.The dependency relationships between the buing rate,tritium breeding ratio,extraction efficiency,and tritium self-suf-ficiency were also specified for the steady state.