Abstract: In this paper, the physical characteristic of the mid-beryllium control rod of HFETR is studied. Firstly, the few group cross section of every assembly is calculated by CELL code. Secondly, the core physical calculations of the setting up control rod cell and mid-beryllium control rod cell are carried out respectively, and the axial thermal flux distribution, the isotope yield and the control rod worth are compared. The result shows that the mid-beryllium control rod can be used for the reactor reactivity control and can improve the reactor’s safety and economy.