Abstract: This paper proposes a calculation model of the failed fuel detection system of China Experimental Fast Reactor （CEFR） based on the experiences from foreign countries and the system design of CEFR. A code using LabWindows/CVI was developed from this calculation model, the minimum broken area which could be detected by the delayed neutron detection system of CEFR was calculated. The calculated data of CEFR and the experimental data of BOR-60 at similar operation condition were compared to validate the fission products’ release model.