Abstract: Accident-tolerant fuel (ATF) is to enhance the accident-tolerant capacity of nuclear fuel by improving the thermal properties of fuel materials or the high temperature oxidation resistance of cladding materials, so that nuclear fuel can endure serious accidents for a long time. Using RELAP5 program developed for ATF, safety analysis of UO₂-FeCrAl, FCM-FeCrAl and conventional nuclear fuel UO₂-Zir-4 was carried out. Compared with conventional UO₂ pellets, FCM pellets with higher thermal conductivity have lower fuel center temperature and smaller radial fuel temperature gradient under steady state operating conditions. FCM pellets also have lower transient initial temperature and lower fuel temperature growth rate under transient accident condition. Compared with conventional cladding Zir-4, the peak cladding temperature of FeCrAl is smaller and reaches later under transient accident condition. Meanwhile, due to the better high temperature oxidation resistance of FeCrAl cladding, the smaller hydrogen mass production is produced during the accident progress.