In this study, the physicochemical properties of the chitin isolated from cicadae (Platypleura kaempferi) periostracum was investigated. The prepared chitin was white flake form and the yield was 31.7%. The chitin was degraded into oligosaccharide during acid hydrolysis at 30oC with concentrated HCl. The hydrolysis rate was 6.8% only after 0.5 h reaction, but increased to 44.0% after 24 h reaction. In distribution of the oligosaccharides in the hydrolyzates, ratio of GlcNAc1-3 content increased from 66.5% after 0.5 h reaction to 84.4% after 12 h reaction. The ratio of monomer GlcNAc content was 79.4% after 24 h reaction and no oligosaccharides bigger than GlcNAc4 was detected. It is found that cicadae periostracum chitin belongs to α-chitin resulting from the FT-IR spectra similar with those of crab and shrimp chitins. In X-ray diffractometer, two peaks were exhibited at 2θ = 9.5o (interplanar distance : 9.36?) and 2θ = 19.4o(4.58?). The crystallinity index and crystal size of the chitin were determined to be 81.9% and 4.6 nm, respectively, which are similar with those of crab and shrimp chitins, again confirming that cicadae periostracum chitin belongs to α-chitin. The degree of acetylation of cicadae periostracum chitin was calculated to be 88.1%.