Objective:To determine the 16S rDNA sequences of 44 strains of Sulfitobacter sp. obtained from the East China Sea and to study their biological activities. Methods:PCR was used to amplify the 16S rDNA sequences of the 44 strains,and the obtained sequences were subjected to GenBank similarity search.The multiple sequence alignment of the 44 strains was done by Clustal X1.8 and MEGA4.1.The antibacterial activities of Sulfitobacter sp. fermentation broths were tested using the following indicator bacteria：Pyricularia oryzae,Bacillus subtills,and Escherichia coli.The cytotoxic activities of the fermentation broths were tested using HL-60 and HepG2 as the indicator cells.ABTS and DPPH antioxidant models were applied to test the free radical scavenging efficacy of the fermentation broth.Results:Analysis of the 16S rDNA genes of the 44 strains showed high similarity (97%-100%) to Sulfitobacter sp..No fermentation broths of the 44 strains showed evident anti-bacterial activities,and they showed different degrees of cytotoxic activities and free radical scavenging capacities.Nineteen strains inhibited the growth of HepG2 cells,with the inhibition rate ranging 6.8%-42.8%; 18 strains inhibited the growth of HL-60 cells,with the inhibition rate ranging 6.9%-43.6%; 12 strains showed ABTS radical scavenging capacity,with the elimination rate ranging 4.49%-23.08%; and 8 strains showed DPPH radical scavenging capacity,with the elimination rate ranging 1.23%-30.76%.Conclusion:The 44 Sulfitobacter sp.strains possess evident cytotoxic activities and free radical scavenging capacities,making them potential for medicinal application and laying a foundation for further development of these bacteria.