Tritium release behavior from Flibe (Li2BeF4) a potential liquid tritium breeding material was investigated. The main chemical form of tritium-containing species in Flibe was controlled to HT or TF by H2 partial pressure and F− potential in an in-pile experimental system. The release rate coefficients of HT and HF, and HT / TF ratio in released tritium under various H2 partial pressure were observed. The mechanism in chemistry change was considered by a model assuming an isotopic exchange reaction. Increase of HT release rate was observed by the addition of Be metal into Flibe. HT permeation rate coefficient through Monel Metal and SUS316 tubing wall contacting with Flibe were smaller by one order of magnitude than HT release rate coefficient.