A　new　alpha-amylase-encoding　gene　(amySL3)　of　glycoside　hydrolase　(GH)　family　13　was　identified　in　soda　lake　isolate　Alkalibacterium　sp.　SL3.　The　deduced　AmySL3　shares　high　identities　(82-98%)　with　putative　alpha-amylases　from　the　genus　Alkalibacterium,　but　has　low　identities　(＜53%)　with　functionally　characterized　counterparts.　amySL3　was　successfully　expressed　in　Escherichia　coli,　and　the　recombinant　enzyme　(rAmySL3)　was　purified　to　electrophoretic　homogeneity.　The　optimal　temperature　and　pH　of　the　activity　of　the　purified　rAmySL3　were　determined　to　be　45　degrees　C　and　pH　7.5,　respectively.　rAmySL3　was　found　to　be　extremely　halophilic,　showing　maximal　enzyme　activity　at　a　nearly　saturated　concentration　of　NaCl.　Its　thermostability　was　greatly　enhanced　in　the　presence　of　4　M　NaCl,　and　it　was　highly　stable　in　5　M　NaCl.　Moreover,　the　enzyme　did　not　require　calcium　ions　for　activity,　and　was　strongly　resistant　to　a　range　of　surfactants　and　hydrophobic　organic　solvents.　The　major　hydrolysis　products　of　rAmySL3　from　soluble　starch　were　maltobiose　and　maltotriose.　The　high　ratio　of　acidic　amino　acids　and　highly　negative　electrostatic　potential　surface　might　account　for　the　halophilic　nature　of　AmySL3.　The　extremely　halophilic,　calcium-independent,　and　surfactant-resistant　properties　make　AmySL3　a　promising　candidate　enzyme　for　both　basic　research　and　industrial　applications.