To study the dynamic behavior of a quayside crane under seismic loads, a transient dynamic analysis method based on the vector finite element theory is proposed. Considering the contact between the quayside crane's gantry wheels and the rails, a dynamic similarity model of the quayside crane is established and subjected to different types of seismic loads. The analysis identifies the locations on the quayside crane that are prone to damage and derailment under seismic loads. The results show that the trapezoidal frame and the front and rear beams of the quayside crane are susceptible to damage during an earthquake, with damage severity increasing toward the free end of the beams. The quayside crane is prone to derailment under strong seismic excitations, with the land-side legs more likely to deform and derail compared to the sea-side legs.