Pile foundations, known for their distinct 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. Finite element numerical analyses were conducted in this investigation to compare the horizontal bearing capacity of rectangular and circular piles with a same cross-sectional area. The horizontal bearing capacity characteristics of rectangular piles were quantitatively analyzed, in which the effects of aspect ratio and filter cake thickness on bearing capacity were investigated. Results demonstrate that under the identical conditions, rectangular piles show an increase in horizontal bearing capacity by over 12%. With the increase of aspect ratio, the improvement ratio in lateral resistance becomes stabilized at around 17%. However, in the presence of filter cake, the horizontal bearing capacity of rectangular pile is lower than that of circular pile 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.