Abstract: Using the current nuclear criticality safety standards in China and MCNP4C code,the nuclear critical safety analysis and evaluation were carried out for UF₆ conversion to uranium metal production line.The nuclear critical benchmark experiment data for international publication were selected,and the deflection and subcritical limiting value with MCNP4C code in the evaluated system were confirmed.The neutron effective multiplication factor for the copper post in the natural condition and accident condition were calculated and analyzed by taking conservative assumptions,and the production line was evaluated according to the comparison of nuclear criticality safety standards.The results show that the subcritical control parameters or the maximum neutron effective multiplication factor is less than the corresponding subcritical limits,and it is in the state of subcritical safety.