Escherichia coli was frequently encountered in the production of southern geese． Different sero-types of E． coli were isolated and cultured． Their biochemical features and serotype were determined．Their toxicities were tested on mice and gosling． The results showed that five serotypes were successfullyseparated． These serotypes were O 114 ，O 26 ，O 119 ，O 126 ，O 124 ． They had different degrees of pathogenicityto both mice and goslings． Among them，O 26 was the most pathogenic，with a mortality rate of 100%．O 119 was the most pathogenic to the goose，reaching 50%． O 124 was the least pathogenic and did not killanimals．