Abstract: A series of laboratory and field studies on the biology, biochemistry, aerology and virolence of the nuclear polyhedrosis virus of E. obliqua,. a key pest of tea gardens in Eastern China, were carried out during-1983-1988 in Wuhan. EoNPV, a member of subgroup A, Baculoviridae, was found to be single embeded with an average viron size of 62×220 nm. It had a specific SDS-PAGE polypeptide map and DNA endonuclease digestion patterns, and distinguished serological features. EoNPV showed no pathogenecity and mutageneclty. to non-target organisms tested either in-vivo or in-vitro. Both laboratory and field tests demonstrated that it had a high toxicity to its host. Techniques of mass rearing E. obliqua with an artificial diet and formulations to protect the virus from sunlight were developed to facilitate the production and the application of the virus as an effective bio-pesticide against E. obliqua in Eastern China.