Abstract: To improve penetrability and bearing capacity of suction foundations in marine engineering, an innovated bionic scaled-steel structure was proposed. After improving traditional interface direct shear apparatus, a series of interface shearing tests of a steel plate continually set with scales in sand and clay were carried out along the cranial and caudal directions respectively, to reveal the variation of residual friction angle and peak shearing stress between the bionic scaled steel plate and soils under different normal stresses. The results showed that: ① the peak shear stress in the cranial direction in sand and clay increased approximately by 14%~65% and 5%~86% compared with the caudal direction respectively. ② When the normal stress was 50 kPa, it was found that the peak shear stress of the scaled interface in sand was 62.41% higher than that of the smooth interface. ③ In clay soil under increasing normal stress and consolidation stress, as the shear direction changed from caudal to cranial, the peak shear stress and residual stress increased and strain softening phenomena was observed. ④ The peak friction angle and residual friction angle of the scaled steel plate and the smooth steel plate in clay had large differences, while the shear direction had little influence. ⑤ In order to reduce friction in penetration construction, it is necessary to weaken the shear effect between soil and steel plates, so the scales should be arranged intermittently at outside of the steel plate. The research results can provide reference for the design of various pile foundations in marine and hydraulic engineering.