The structures and fibrous composition of egg case of the spider (Argiope bruennichi) were examined using SEM as well as amino acid analysis. The egg case is composed of multiple layers of silk, including the frame, outer cover, cover cap, inner cover, egg cover cap and egg wrapping cover, and formed by different colored silk with diameters between hundreds of nanometers and several micrometers. The amino acid composition was similar in the frame silk and typical dragline silk, glycine (about 37%) and alanine (about 25%) are the most abundant amino acids present, and glutamic acid (about 10%), prone (about 7%) and serine (about 5%) as the next most abundant. The amino acid composition of cover silk was similar with typical cylindrical gland silk. In contrast to the frame silk, all cover silk of egg case contained a significant proportion of the serine (about 22%) and less glycine (about 7%) and prone (about 2%), and contained more polar amino and large side acids. The original gland that produce silk fibers with different diameters was analyzed based on the results of SEM and amino acid composition studies.