The salt of[Mn（H₂O）₆]（NTO）₂·2H₂O was prepared by mixing the acqueous solution of lithium 3-nitro-1,2,4-triazol-5-onate and manganese（Ⅱ）sulfate.It was characterized by thermal analysis,elemental analysis and IR measurement.The crystal structure of[Mn（H₂O）₆]（NTO）₂·2H₂O was determined by a single crystal diffraction analysis.The crystal belongs to space group C2/C with crystal parameters of α=23.423（3）Å,b=6.5262(9)Å,c=19.412(3)Å,a=90.00(0)^。,ß=142.713^。,γ=90.00(0)^。,v=1797.6(4)ų,Z=4,D_c=1.70g.cm^-3,μ=7.87cm^-1,F（000）=947.75。