To investigate the influence of fault structures and structural planes on the failure modes of high and steep open-pit slopes,with a lithium polymetallic mine in Hunan Province as an engineering background,the study conducted field surveys and theoretical analyses. The mine area is characterized by a near-SN main fault structure,along with NE fault zones,near-EW fault,NW faults,arc-shaped faults,and various joint fissures forming the basic structural framework of the mining site. Field investigations revealed the occurrences of rock structural planes,and statistical analyses identified dominant structural planes:3 sets in coarse to medium-grained porphyritic biotite granite,2 sets in medium to fine-grained porphyritic biotite granite,and 2 sets in greisen. Stereographic projection analysis was employed to assess the impact of fault structures and structural planes on high and steep open-pit slope failure modes. Results indicate that the F2 fault structure may cause planar failure in Zone Ⅳ；only the third set of dominant structural planes in coarse to medium-grained porphyritic biotite granite may result in planar failure in Zone Ⅲ；and wedge failure may occur in Zones Ⅲ and Ⅳ due to combinations of the second and third sets of dominant structural planes intersecting the slope face.