The pathological changes of digestive organs were observed by optical microscopy and electron microscopy at the 3rd,5th,7th,9th,and 11th day after artificial infection of Hyriopsis cumingii with the pathological tissue liquid.The results showed that the H.cumingii Plague virus damaged the structure of the digestive organs.The liver was most seriously damaged.This digestive gland was swelling and its lumen was smaller at the 7th day of infection,and after that vacuolation and coenocytes were observed.Under electron microscope,the organelles such as mitochondria and endoplasmic reticulum were damaged and the virus particles were frequently observed.Pathological changes also included stomach and intestine damages.Their structure damage was not obvious within 7 days of infection,but after the 7th day the columnar cells became swellen and the cilia were detached from the epithelial cells.Under electron microscope,organelles damage and even vacuolation were observed.The virus particles became more frequently observed at later stage of infection,but less than observed in the liver.