The most abundant neuropeptide, crustacean hyperglycemic hormone （CHH） has been first extracted from sinus glands of Eriocheir sinensis, and purified to homogeneity by reverse-phase high performance liquid chromatogram （RP-HPLC）. The sinus glands of Eriocheir sinensis are the organs to store neuropeptides, which are quite perfect to do research for the neurosecretory system of Eriocheir sinensis. For the crab Eriocheir sinensis, CHH accounts for （ 153.63 ? 32.23） ng（n = 4） per SG, while the extracts of one sinus gland reach （ 1252.63 ? 298.40） ng（ n = 4）. In crustaceans, the CHH and the structurally related peptides MIH （ moltinhibiting hormone）, VIH （ viteUogenesis inhibiting hormone） and MOIH （ mandibular organ inhibiting hormone）, are classically considered as the major physiological regulators involved in the control of carbohydrate metabolism and in different functions such as molt, reproduction and hydromineral metabolism. The amino acid sequences of these neuropeptides hormones are similar to each other： they consist of 72 - 78 residues with six conserved cysteine residues arranged in three disulfide bridges. CHH shows obviously hyperglycemic activity, which can make the haemolymph of the crab Eriocheir sinensis reach the highest level （56.14 ? 10.58） mg?100 mL^- 1 ） only in 30 minutes, while the CHHs from any other species that have been examined show hyperglycemic activity in about 2 hours. The molecular weight of CHH was examined by SDS-PAGE under the indication of protein Marker （BBI, from 4.1 kD to 66 kD）, the result was 5.1 kD with the use of GDS Microsoft to analyze, which is much lower than any other CHH （7 - 9 kD） that has already been known. In recent years, the amino acid sequences of the CHHs from many species of orustaceans have been determined, however, no sequence data for CHH from Eriocheir sinensis has been reported so far, and will be reported later. In this paper CHH from Eriocheir sinensis has been separated and its biological activity has been examined, the results of the experiment will be helpful for the further research in the synthesis and secretion of the neuropeptides, as well as have laid the foundation to determine the physiological function of other neuropeptides hormones in the sinus glands.