Abstract: Tritium, as an inherent detrimental byproduct of molten salt reactor (MSR), featured with corrosivity and permeability, is one of the most critical problems confining the development of MSR. In this paper, tritium transport characteristics for fluoride-salt-cooled high-temperature reactor (FHR) were analyzed including tritium production rate, graphite absorption, and tritium dissolution in molten salt, corrosion and deposition reactions as well as T₂ diffusion, under transients such as unprotected reactivity insertion (URI) accident and unprotected overcooling (UOC) accident. It is found that tritium transport characteristics become much more complicated under transient conditions than steady state, and they are strongly coupled with each other, bringing higher requirements for the performances of the tritium control equipment. Furthermore, the rates of T₂ diffusing to the secondary loop both decrease under URI accident and UOC accident, averting the operation of extra safety facilities for tritium control.