Abstract: Micropterus salmoides was one of the chief fresh water rearing breed in China. As a result of rearing scale enlarging and intensive degree improving,the disease occurred frequently. Especially in the lately year large-scale Micropterus salmoides died repeatedly in the reservoir cage culture in Fenghua and Ninghai of Zhejiang province,which caused a large loss for the breeding. Much slime around the body of fish was an important sign of the diseased fish. At the beginning of disease,the fish body color started to become deep,and exercise ability decreased,and float on the surface of the water. When the disease became systemic,fin would be bloody and ulcer,and the scales of some diseased fish dropped seriously,and some fish body had parasitic saprolegnia. The gut would be diseased,the stomach and intestines would be bloody,liver would be yellow spot. The fishes would be dead in seven days after the symptom began. Because the symptom of diseased fish was similar to that of the white cloud disease of carp,this disease was called the white cloud of Micropterus salmoides. The white cloud disease was one of the best harmful disease in carp rearing in the world. This disease was firstly found in 1973 in Japan. At 1980's,this disease was reported in carp rearing in some areas of China, but this disease was firstly found in Micropterus salmoides rearing. The disease occurred between winter to spring,with the water temperature below 18℃. In the reservoir cage culture of Micropterus salmoides, the total infection rate was 80% and mortality was from 50%to 70%. Micropterus salmoides in the ponds had never been found the white cloud disease. If the diseased fish was placed in the pond and was eaten by bait adding vitamin C,the diseased fish would recover. Diseased fish and health fish came from the rearing reservoir in Fenghua of Zhejiang province,and the fishes weighed from 250g to 500g in the study. One strain of bacteria 01314-1 was isolated from the white cloud disease of Micropterus salmoides,which was dying. After the pure culture,the artificial infection was done to the health Micropterus salmoides, the ways of the artificial infection had three: abdominal cavity (0.3mL/nos),wound soaking,and soaking. The concentration of bacterial suspension was determined by McF and live bacterial counting technique. The control was substitute for physiological saline. The concentration of soaking was 2.31×10 5 Cells· mL-1 . The result showed that the strain of bacterial 01314-1 had powerful pathogenicity and the mortality of health fishes was 100%. The symptom of the artificial infection fishes was similar to that of the natural diseased fish,and one strain of bacterial which was isolated from the slime,blood,liver,kidney of the artificial infection fishes was the same to bacterial 01314-1. According to Bergey' manual of systematic bacteriology and API 20NE system indentification,the pathogen of Micropterus salmoides was identified Burkhol cepacid. Burkhol cepacid often occurred in sea and oil,which caused many disease of human and animal. The main sign was septicaemia,infection and abscess. Serum was made of the blood from diseased fishes and health fishes,which of the blood biochemical indices was determined by DADE BEHRING biochemical automatic instrument. Compared with healthy fishes,the blood biochemical indices showed that serum enzymes of ALT,AST,LDH and the number of total protein,urea nitrogen,creatinine,K + of diseased fishes all increased remarkably,but the contents of glucose,cholesterol,Na +,Cl-decreased. The results indicated that the liver,kidney,and muscle of the fishes had diseased and many important physiological functions were seriously destroyed,after micropterus salmoides was infected. The increasing of total protein,urea nitrogen and creatinine in the serum showed that the fish body lost water and the blood concentrated,which was accord with the phenomenon of a lot of slime with the diseased fish. The way of the drug sensitivity test was the same to the others,and the Chinese herbal medicine paper was r