On January 3，2020，some pigs showed diarrhea in a farm，followed by a peak three days later，accompanied by the death of some pigs across the farm，and the rates of infection and fatality were 60.66% and 6.88%，respectively. The outbreak was investigated by combination of field investigation and laboratory test，and it was concluded that the diarrhea outbreak was caused by bacterial infection of Escherichia coli，Salmonella and Shigella，as well as by the stress. The main reasons of the outbreak were drinking waste water，stress due to stopping water and cold weather. In view of the above，some measures were applied，such as mixing antibiotics with feed，cleaning and disinfecting pig houses and drinking facilities，and strengthening feeding management，then the outbreak was effectively controlled. According to the investigation，it was of great significance for swine diarrhea prevention to strengthen feeding management，reduce stress caused by cold and lack of water，and to maintaining clean drinking water.