Abstract: Molten salt reactor is the only liquid fuel reactor in the fourth generation nuclear energy system, so-called as “chemical reactor”. There are many key issues directly related to chemistry in the development and operation of thorium based molten salt reactor. Due to the needs of the development and operation of molten salt reactor, a new branch of radiochemistry in the utilization of fission energy has emerged—molten-salt-reactor chemistry. Study on the molten-salt-reactor-chemistry has begun to carry out in our laboratory by using the photo-neutron source driven by an accelerator and the γ-ray spectrometry. Progresses of the study were introduced on distribution and behaviors in FLiBe melt for the intermediate nuclide of thorium-uranium convert ²³³Pa, fission products ¹³¹I and ⁹⁵Nb in this paper. In view of the issues drawn from the molten salt reactor experiment (MSRE) operated by ORNL, future research items recommended in the frame of the molten-salt-reactor-chemistry were proposed, i.e. chemical monitor and diagnosis in the operation of TMSR, factors of the effect on redox potential of melt, and a new techniques of monitoring redox potential for melt. The further deepening of research on molten-salt-reactor-chemistry will expand the practice and theory of molten-salt-reactor-chemistry, elevate the chemical level of thorium based molten salt reactor to new heights, and provide scientific and technological support and guarantees for the efficient and safe operation of thorium based molten salt reactors in the future.