Abstract: In order to explore high-efficiency sulfur-oxidizing strains from mariculture environment, a marine sulfur-oxidizing bacterium, designated as strain B2-1, was isolated from the offshore sediment of culturing area of Meizhou Bay, Fujian Province. The morphological, physiological properties and 16S rRNA gene sequence, as well as the thiosulfate oxidizability under different culture conditions were analyzed. Strain B2-1was a Gram-negative, short rod bacteria and motile with a single polar flagellum.16S rRNA gene sequence analysis indicated that strain B2-1 was most closely related to the Thiomicrorhabdus indica 13-15AT (100% sequence similarity), thus designated as Thiomicrorhabdus sp. B2-1. The thiosulfate oxidation of strain B2-1 was observed at pH ranging from 6.0 to 9.0 (optimum, pH 8.0) and temperatures from 20 to 35°C (optimum, 30°C). The oxidation ability of strain B2-1 increased first and then inhibited with the increase of Mg2+concentration, with the optimum concentration of Mg2+ as 50 mmol/L. The addition of NH4+ could shorten the lag period and enhanced the oxidation ability. The oxidation rate could raise from 47.4% to 95.5% with the addition of 187 mmol/L NH4+（P<0.05）. Thiomicrorhabdus sp. B2-1 has great application potential for sulfur oxidation in mariculture environment control.