Abstract: The micro-structure of elytra was observed by SEM. The nano-mechanical property of elytra was tested and analyzed with a nano-indentation machine. SEM images indicate that the elytra of Allomyrina dichotoma are lightweight biological composites with a hollow structure like as arch shape. The duty ratio of cross-section is 26.36%. The elytra are composed of epicuticle(EPI) and exocuticle(EXO). The exocuticle consists of 11~12 fiber layers, laying in quadrature manner with a ply angle 45? plus lots of fibrils braiding across, which form a laminated plate structure. The hardness, modulus and contact stiffness of epicuticle in elytra acquired with nano-indentation testing are (0.28?0.13) GPa,(5.62?1.21) GPa and (1.67?0.14)?10⁴ N/m, respectively. The nano-mechanical properties of elytra present a topological distribution characteristic, namely is a gradually incremental tendency from the cephalosome zone to the empennage zone. The results may provide biological template and biomimetic theory to design a new lightweight bionic structure inspired by the elytra in beetle Allomyrina dichotoma for the further researches.