A Gram-negative rod bacteria isolated from the hydrocardia of a hydropericarditis patient was reported. Maincharteristics of the strain are respiratory metabolism, oxidse positive and motility by one polar flagella. Through systematic morphological, physiological and biochemical identification; calculation of G+C mol%, and examination with Biolog Automated Systems, the species of Pseudomonas vesicularis are identified. We pointed out that the strain can infect an immuno-suppressed individual. The change of taxonomic position of the species was discussed.