Abstract: The supercritical water-cooled reactor fuel qualification test (SCWR-FQT) intends to test a small scale fuel assembly under supercritical water environment in a research reactor. For the safety system design and safety analysis of the test loop, the modified ATHLET code was applied to model the loop, and simulate two design basis accidents, which caused partial or total loss of coolant flow in the fuel assembly test section. The calculated accidents were coolant bypassing the test section due to cracks in the internal structures of the pressure tube, and primary pump seizure. The calculation results show that, in the first accident the fuel cladding temperature shows a peak value of about 920 ℃ in the early stage of the transient, while in the second accident the fuel cladding temperature suffers no obvious increase. It is suggested by the results that the current safety system design is able to provide effective cooling to the test section in the two simulated accidents.