Pile foundations, known for their favorable horizontal load-bearing characteristics, are widely utilized in excavation support systems for foundation construction. In comparison to circular piles with equal cross-sectional areas, rectangular piles exhibit superior resistance to horizontal loads. This study conducts numerical analyses to compare the horizontal bearing capacity of rectangular and circular piles with the same cross-sectional area. The horizontal bearing capacity characteristics of rectangular piles are quantitatively analyzed, in which the effects of aspect ratio and filter cake thickness on bearing capacity are investigated. The results demonstrate that under the identical conditions, rectangular piles exhibit an increase in horizontal bearing capacity by over 12%. As the aspect ratio increases, the improvement ratio stabilizes at around 17%. However, in the presence of filter cake, the horizontal bearing capacity of rectangular piles is lower than that of circular piles with the same cross-section. Thus, appropriate measures should be implemented during the on-site construction of rectangular piles. This study provides valuable insights for future construction of rectangular piles.