Abstract: The pile-supported wharf is a common type of coastal structures, and the slope of pile-supported wharf may experience the overall instability and large lateral deformation during earthquakes. The upper bound limit analysis method is used to assess the pseudo-static stability of a slope of the pile-supported wharf. The stability effects of pile rows on the slope is simplified to a trapezoidal distributed force, the critical seismic coefficient is derived using the log-spiral failure mechanism, and the minimum upper bound solution for the critical seismic coefficient and the corresponding critical slip surface are determined through optimization. To verify the rationality, the results obtained from the proposed method and the finite element limit analysis are compared through a specific exmple. Furthermore, combined with the strength reduction method, the influences of row-pile arrangement and soil strength on the seismic stability and failure mechanism of the slope are obtained.