An explosive epidemic disease of shrimp occurred in 1993. The pathological study on diseased shrimp through light and electron microscope examination showed that inflated and deeply eosinophilic nuclei were found in the following tissues: Hypodermal tissue (including epithelium of fore and hindgut, epidermis and gill, etc.), connective tissue hematopoietic tissue, antennal gland and hemolymph cells as well. Under electron microscopy, pathogenic nuclei were fully filled with a kind of baculovirus, which was 120nm*360nm in size and covered with envelop. Because no polyhedron and gramlin were discovered in nuclear, the virus belonged to C group baculovirus, i.e. non-occluded baculovirus. According to the epidemic symptom, infected target tissue and characteristics of virus, the virus was considered a new shrimp virus and named hypodermal and hematopoietic necrosis baculovirus (HHNBV) temporarily.