Abstract: In order to study the transient response of power change in liquid metal coupled natural circulation loops and their stability, a model for analyzing coupled natural circulation loops was established based on the single lead bismuth eutectics (LBE) natural circulation loop by using SIMULINK, and FLUENT code was used to validate the model. The flow oscillations during different processes of increasing power and decreasing power were analyzed. Meanwhile, the stability of coupled loops was also studied. The results show that extending the time for increasing power can reduce the flow oscillations. Furthermore, increasing power more slowly at the beginning will be better for reducing the flow oscillations and the time required to reach steady state. Obvious flow oscillations are not observed in coupled natural circulation loops when the rate of power decrease is different, so the power decrease rate will not influence the stability apparently. Coupled natural circulation loops are more unstable than single loop. On the other hand, they can be stabilized by decreasing the thermal resistance of the intermediate heat transfer surface.