Bacillus mojavensis B0621A was isolated from the mantle of a pearl oyster Pinctada martensii collected from South China Sea. Semi-purified surfactins (225 mg L-1) were obtained by acid precipitation and vacuum flash chromatography. The component of the semi-purified surfactins was preliminarily analyzed by liquid chromatography mass spectrometer system, and the results showed that all these surfactins could be a group of homologues. Eight surfactin homologues were isolated and afforded by reversed phase high-performance liquid chromatography. Furthermore, their structure was characterized by mass spectrometry analysis combined with nuclear magnetic resonance spectroscopy techniques. These surfactins shared seven amino acids as peptide backbone and a saturated beta-hydroxy fatty acid chain residue (from C-13 to C-15), differed each other from peptide sequence in the position of Leu(7) or Val(7). All these surfactins had significant activity and stability of emulsification under various pH (from 7.0 to 12.0), temperature range (from 20 to 115 A degrees C) and sodium chloride concentration (from 2.5 to 20.0 %, w/v). Taken all together, these results indicated that B. mojavensis B0621A have potential to be an alternative source as a biological-derived emulsifying agent.