[K(NTO)(H2O)] was prepared by mxing the aqueous solution of 3-nitro-1, 2, 4-triazol-5-onate (NTO) and potassium hydroxide and characterized by TG, elemental analysis and IR measurement. The crystal structure of [K(NTO)(H2O)] was determined by single crystal diffraction analysis. The crystal is monoclinic, space group P21/n with crystal parameters of a=0.6408(1), b=0.8218(1), c=1.2626(1)nm, β=100.63ⅲ(1), V=0.6535(1)nm^3, Z=4, Dc=1.892g.cm^-^3, μ=0.785mm^-^1, F(000)=376. The final R is 0.0246. The EHMO calculation shows that the title compound forms a complex mainly through static electric attraction force. K atom combines more strongly with NTO ring than with H2O, which predicts that H2O has the priority to leave when [K(NTO)(H2O)] is heated.

Key words: NITRO COMPOUNDS, INFRARED SPECTROPHOTOMETRY, ELEMENTAL ANALYSIS, CRYSTAL STRUCTURE, THERMOGRAVIMETRY, PYRRODIAZOLE P, KETONE P