Based on the dimensional analysis theory, in this paper, we propose a similarity criterion for the dynamic response of a scaled polar crane in a nuclear power plant under earthquake action. We determine the similarity relation of dynamic responses between a prototype nuclear polar crane and the scaled model. As the shaking table input, we used the El Centro wave, and based on the seismic code requirement and similarity criterion, we scaled the input amplitude to 0.3g and 0.2g in the horizontal and vertical directions, respectively, with a time scale of 4. Comparing the maximum accelerations of the shaking table inputs, the scaled model experiment results showed that the peak acceleration in the middle-span of the crane girder increases 56.0% in the horizontal direction and 119.0% in the vertical direction, and the peak acceleration in the polar girder increases 66.7% in the horizontal direction and 43.5% in the vertical direction. These experimental results indicate that when the direction of the earthquake input is vertical to a crane girder, the horizontal peak acceleration in the middle span of the crane girder is maximum. When the earthquake input is parallel to the crane girder, the horizontal peak acceleration in the polar girder is maximum. The influence of the direction of the earthquake input on the vertical peak acceleration in polar girder is not significant. Under earthquake loading, the polar crane experiences no derailing phenomenon.