A summary of the tritium system design activities for the engineering outline design of a fusion experimental reactor [Fusion Experimental Breeder-E (FEB-E)] is presented. This paper is divided into three sections. First, the geometry, loading features, and tritium concentrations in liquid lithium of tritium breeding zones in blankets are described. Then, a tritium flowchart corresponding to the tritium fuel cycle system is constructed, and the SWITRIM code is developed for calculation of the inventories in the ten subsystems. Results show that the necessary initial tritium storage to start up the reactor with fusion power of 143 MW is ~317 g. Finally, a tritium leakage analysis under different operation circumstances is performed. It is found that the potential danger of tritium leakage could result from the exhausted gas of the divertor system. It is important to elevate the tritium burnup fraction and reduce the tritium throughput.