<p>The scaled suction caisson represents an innovative design featuring a bio-inspired sidewall modeled after snakeskin, commonly utilized in offshore mooring platforms. In comparison with traditional suction caissons, this bio-inspired design demonstrates reduced penetration resistance and enhanced pull-out capacity due to the anisotropic shear behaviors of its sidewall. To investigate the shear behavior of the bio-inspired sidewall under pull-out load, direct shear tests were conducted between the bio-inspired surface and sand. The research demonstrates that the interface shear strength of the bio-inspired surface significantly surpasses that of the smooth surface due to interlocking effects. Additionally, the interface shear strength correlates with the aspect ratio of the bio-inspired surface, shear angle, and particle diameter distribution, with values increasing as the uniformity coefficient <i>C</i>_u decreases, while initially increasing and subsequently decreasing with increases in both aspect ratio and shear angle. The ratio between the interface friction angle <i>δ</i> and internal friction angle <i>δ</i>_s defines the interface effect factor <i>k</i>. For the bio-inspired surface, the interface effect factor <i>k</i> varies with shear angle <i>β</i>, ranging from 0.9 to 1.12. The peak value occurs at a shear angle <i>β</i> of 60°, substantially exceeding that of the smooth surface. A method for calculating the relative roughness <i>R</i>_N is employed to evaluate the interface roughness of the bio-inspired surface, taking into account scale dimension and particle diameter distribution effects.</p>