Abstract: A study was conducted to determine the serological relationships between strains of Pseudomonas solanacerum in China. Four corresponding antisera were prepared to a kind of membrane protein extracted from cells of four strains representing different biotypes of P. solanacerum respectively. By using Ouchterlong double diffusion tests, 212 isolates from ninteen different hosts in six provinces and cities could be grouped into eight serotypes. It was demonstrated that 147 isolates of them belonged to serotype I which was the predominant one (69%) including thirteen various hosts. SDS PAGE profiles of mebrane proteins extracted from strains representing eight serotypes of P. solanacerum showed that there were some differences between serotypes.