Abstract: The development of Tokamak fusion reactors encompasses hybrid and pure fusion reactor designs. In the study of tritium self-sustainability, the average retention time method is predominantly employed for Tokamak fusion reactors, with less emphasis on hybrid reactors. To enhance research in this area, this paper employs a more realistic integral analysis method to examine the requirements for startup tritium inventory and tritium breeding ratio(TBR) necessary to achieve tritium self-sustainability in both hybrid and pure fusion reactors. The findings demonstrate a linear relationship between startup tritium inventory, backup tritium inventory, and fusion power, while the required TBR is inversely proportional to the fusion power. Notably, the reserve tritium inventory plays a significant role in determining startup requirements for hybrid reactors. Within the range of 50-450 MW fusion power, a TBR above 1.15 is needed; particularly below 100 MW fusion power level where it reaches 1.4-posing substantial engineering challenges. The impact of initial levels of startup tritium on required TBR in hybrid reactors is negligible; however, reducing long-term tritium retention can help lower TBR requirements. For pure fusion reactors as well, it is observed that reserve tritium constitutes most of the startup inventory with tens of kilograms being necessary; therefore, considering redundant design or improving maintainability and reliability should be explored to reduce reserve tritium. Furthermore, achieving a required TBR below 1.15 appears more feasible within a range of 1-5 GW fusion power for pure fusion reactors. This paper further examines the impact of operational factors on the required TBR, and the study demonstrates that operational factors are an essential prerequisite for achieving tritium self-sustainability. To emphasize the influence of operational factors on tritium self-sustainability, this paper proposes a redefined relational equation for assessing tritium self-sustainability in fusion reactors.