Abstract: The aim of this study was to explose relatioship between outer menbrane protein and virulence of Haemophilus parasuis. The outer membrane proteins (OMP) of 82 isolates of Haemophilus parasuis were determined by SDSPAGE. We compared the diversity of the OMP phenotype of isolates from diffent clinical background to explore the associativity between OMP and virulence pathogen, and analyzed relationship between the OMP and virulen isolates by cluster analysis based on Rf of electrophoresis and contents of OMP. The results of analysis of OMP phenotye showed that isolates were divided into two major PAGE type groups as differece of Rf. PAGE I was characterized from 36 to 40 kD OMP and PAGEⅡwas characterized 4245 kD OMP, and included about 34% isolates recovered from disease pigs and 8.7% isolates recovered from healthy pigs belong to PAGE I; PAGE II was characterized by absence of the 3640 kD proteins. The result of cluster as Rf indicated that isolates were divided into three types: PAGEⅠ, PAGEⅡand PAGEⅢ. Analysis of cluster as contents of OMP obtained five classsifications of isolates. It is prompted that the 3640 kD OMP was correlated with virulence.