Abstract In the present study, a series of numerical simulations were conducted to analyze the dynamic behavior of an engineering ship with mooring line failure. For this purpose, a fully coupled dynamic analysis program was used to develop a nonlinear numerical model of the hull-mooring system. One of the four mooring lines was intentionally disconnected at a certain time. Under the environmental condition, the ship motions and mooring line tension were discussed in detail. It turned out that mooring line failure would have a significant influence on the performance of the ship, which may threaten the safety of the floating system. In addition, the transient effects of mooring line failure caused the transient overshoots of the ship motion and mooring line tension. Therefore, it is necessary to study the effects of mooring line failure on the floating system in advance.