The embodiment of the invention discloses a three-dimensional structure unit for forming a novel truss structure. The unit comprises first to fourth groups of two-dimensional frame units which are sequentially axisymmetric. Each of the first to fourth groups of two-dimensional frame units comprises a first parallelogram unit, a second parallelogram unit and a third parallelogram unit which are sequentially connected from top to bottom, and adjacent edges of the first and second groups of two-dimensional frame units and the third and fourth groups of two-dimensional frame units are connected. The third parallelogram units of the first to fourth groups of two-dimensional frame units are connected in sequence. Ridge edges are formed by connecting edges of the first parallelogram unit and thesecond parallelogram unit, and valley edges are formed by connecting edges of the second parallelogram unit and the third parallelogram unit. The embodiment of the invention further provides a novel truss structure and a design method. The structure provided by the invention is high in porosity, has ideal rigidity, yield strength and ultimate compressive strength under the condition of the same porosity, and has relatively strong energy absorption capability and anisotropic mechanical properties.