Abstract: In hubei province,there were 180 piglets diarrheaed in certain pig field. The dead weaning brash piglets were autopsy and observed that some tissue occured cheese pathological change. And plasma membrane had different level bleeding point all over the body. We found that bowels wall was thickness and elasticity decreased. Then selected randomly serious weaning brash piglets were 10 and normal piglets were 3. From their content of intestinal tract, 7 strain bacteria were isolated and cultured. In order biochemistry identited they were salmonella typhisuis, Bacterium aerogenes, Escherichia, pneumonia bacillus, Bacterium vulgare of Proteus, Shigella. The percentage in piglets diarrheaed were 87.5%,57.1%,100%,28.6%,28.6%,14.3%,28.6%.Through pathogenicity testing on mouse the difference of pathopoiesis were 100%,.60%,10%,20%,40%,60%,80%. It was concluded that salmonella typhis was the main pathogenic bacteria in the field. 

Key words: weaning brash piglet; pathogenic strain; identification; salmonella typhis