In order to characterize the property of metabolic substances of salt2resistant Rhodospirillaceae bacteria , the aseptic metabolic substances were purified by column chromatography on CM -Sephadex C -50. Three protein peaks : PSB2 -1’, PSB2 -2’, PSB2 -3’were obtained. The protein peak of PSB2 -1’had inhibiting activity against the pathogens. The antibacterial protein peak of PSB2-1’was confirmed as electrophoresis purity with SDS -PAGE. Only one band was shown when antibacterial protein was checked by capillary zone electrophoresis. And the molecular weight of antibacterial protein was 9290 Da checked by mass spectrometry. The antagonistic products produced by salt2resistant Rhodospirillaceae bacteria were heat2stable and were not sensitive to ultraviolet radiation , but sensitive to acidity and alkalinity. And the inhibitory activity was influenced by treatment with trypsin , pepsin and subtilisin. The antagonistic substances produced by salt2resistant Rhodospirillaceae bacteria could be preliminarily classified with small heat2stable peptide (SHSP) .