The　yield　surfaces　and　the　evolution　of　yield　surfaces　of　a　bending-dominated　pyramidal　lattice　material　under　complex　stress　states　considering　the　coupling　effect　of　axial　force　and　bending　moment　of　a　strut　are　studied　theoretically.　The　two-dimensional　primary　yield　surfaces,　secondary　yield　surfaces,　and　complete　yield　surfaces　of　pyramidal　lattice　materials　of　two　kinds　of　cross-section　struts　are　obtained,　and　the　analytical　expressions　of　yield　surfaces　are　established.　The　effects　of　the　inclination　angle　and　diameter-to-length　ratio　of　the　struts　on　the　yield　surfaces　of　pyramidal　lattice　materials　with　circular　cross-sections　are　discussed.　The　results　provide　a　basis　for　analyzing　homogenized　plastic　properties　of　complex　lattice　material　structures.