Abstract: Otis undulata macqueenii and Otis tarda tarda are rare and endangered species in the world,and listed in the first category protected animal in China.This paper deals with our studies on the ultrastructural eggshell of these two species with scanning electron microscopy. The microstructures of the eggshell of O.u.macqueenii and O.t.tarda are composed chiefly of inner shell membrane,outer shell membrane,cone layer,spongy layer and outer layer.Their characteristics are following: 1) Outer eggshell membrane layer Under the scanning electron microscopy the outer shell membrane of both species appear dense mat fibre with some bud projections and interweave into net and arrange in many layers.There is also obvious difference between these two species.The diameter of the membrane fibre of O.t.tarda is wider than that of O.u.macqueenii,but the membrane fibre of O.u.macqueenii is much compacter than that of O.t.tarda.In addition,the bud projections on shell membrane fibre of O.u.macqueenii are more profuse than those of O.t.tarda.2) Cone layer The cone knobs of the eggshell of O.u.macqueenii are arranged thickly in flower shape,while those of eggshell of O.t.tarda are arranged loosely in different shape and size and consist of several cone cores.3) Spongy layer The spongy layer is the hardest part of the eggshell.There are many gas-filled vesicular hole in this layer.4) Outer layer The outer surface of the eggshell of both Otis undulata macqueenii and Otis tarda tarda is rough and has many granules and many pore mouths in various size and appearance.The granules on the outer surface of eggshell of O.u.macqueenii are more than those of O.t.tarda.The pore mouths of the latter are less than those of the former,but larger.There is a protein membrane produced by oviduct to prevent bacterium and water loss.Results of the energy spectrometer show that the element component of eggshell is related with the habitat as well as the food.