Abstract: The maintainability of the nuclear containment vessel/polar crane coupling system under strong earthquakes is one of the key factors affecting nuclear safety. In order to reveal the influence of stick-slip effect on the seismic performance of the system, the modified LuGre model is used to build the frictional effect between the drive wheel and the track. A linear complementarity problem is introduced to describe the no smooth contact of stacked parts, on this basis, the rigid-flexible coupling dynamic model of polar crane considering multi-point frictional contact is established. The representative strong earthquake records are selected as the bedrock ground motion, and the transient response under multiple conditions is analyzed to reveal the seismic response mechanism of the coupling system. Numerical results show that: the friction between the brake wheel and the track is the key to maintain the system in a desired position, and the stick-slip effect must be considered in the dynamic model. The derailment behavior is affected by three-directional earthquakes, strong horizontal earthquake and weak vertical earthquake can also induce derailment. Instantaneous derailment induces instantaneous impact, the peak wheel pressure can reach 10 times of the static wheel pressure, the peak tension of the main hook reaches 2.5 times of the static tension, and vibration isolation device shall be installed to avoid wire rope breaking.