Abstract: With the development of large equipment manufacturing and aerospace engineering, trusses play more and more significant roles in structural lightweight design. For different bearing requirements in each direction of truss structures, bearing characteristics of a tri-prism straight truss are studied with the continuum equivalent method. Based on the principle of energy equivalence, the configuration of the cross section is considered, the discrete truss is equivalent to a beam of a continuum model, the equivalent stiffness and mass of the beam model are obtained, and the numerical frequencies are compared with the theoretical results to verify the equivalent calculations. The changes of transverse bending stiffness and frequency are investigated with different side ratios in the cross section of a tri-prism truss. The influence on transverse bending stiffness and frequency of the tri-prism truss is studied by changing the configuration of the truss units. The research has certain guidance significance for applying truss structure in engineering fields.