Abstract: Objective To investigate the distribution and antibiotic sensitivity of the bacteria in the seawater of Xisha in the South China Sea. Methods The samples of the seawater in Xisha were collected for bacterial counting, identification and antibiotic sensitivity tests. Result Of the 84 bacterial strains isolated from the 80 seawater samples, 38 (45.24%) belonged to Vibrio alginolyticus, 11 (13.10%) to Sphingomonas, 9 (10.72%) to Comamonas terrigena, 7 (8.33%) to Werepseudomonas, 6 (7.14%) to Moraxella, 5 (5.95%) to Cedeceadavisae, and 8 to other bacteria including 2 Aeromona, 2 Acinetobacter, 1 Pantoea agglomerans, 1 Kingella kingae, 1 Shewanella putrefaciens and 1 Suttonella indologenes. Tests of the antibiotic sensitivity showed that all the bacteria were high sensitive to 16 kinds of the antibiotics with the exception of Vibrio alginolyticus, Sphingomonas and comamonas terrigena that were less sensitive to aztreonam or piperacillin and Sphingomonas to cefotaxime or cefepime. Conclusion The investigation will be of great significance for early-stage prevention and cure of bacterial infection acquired from the seawater.