A new complex hexaaquamagnesium(Ⅱ) bis [2-(thiosemicarbazonomethyl)-benzoato],has been prepared and characterized by elemental analysis,IR spectra,molar conductivity and single-crystal X-ray diffraction. The results of crystal structure show that each Mg(Ⅱ) ion is coordinated with six oxygen atoms from water molecules and the complex formed two dimensional layered structure through intramolecule and intermolecule hydrogen bonds. The antibacterial assay of the magnesium(Ⅱ) complex and the ligand were tested using a modified version of the 2-fold serial dilution method,the results show that the complex show considerable antibacterial activity against escherichia coli,bacillus subtilis and staphylococcus white,and the ligand did not show antibacterial activity.