Ammonium 5-sulfosalicylic acid monohydrate(NH4·C7H5O6S·H2O, ASSA) was synthesized and optical grade crystal with dimensions of 45 mm × 20 mm × 18 mm was obtained from aqueous solution by the cooling solution method. The crystal structure was confirmed by X-ray single-crystal diffraction method and the empirical composition is C7H11NO7 S with formula weight 253.23. The crystal belongs to monoclinic space group P21/c with a = 11.884(9), b = 7.306(5), c = 12.152(9) , β= 104.851(13)°, V = 1019.8(13) 3, Z = 4, Dc = 1.649 g/cm3, μ = 0.340 mm-1, F(000) = 528, the final R = 0.0307 and w R = 0.0866 for 7494 observed reflections(Ⅰ > 2δ(Ⅰ)). Elemental analysis, IR and 1H-NMR spectrum were used to characterize the compound. Thermal analysis showed that one coordination water molecule was contained and dehydration temperature of ASSA crystal was 106℃. Optical transmission and fluorescence spectrum revealed that the ASSA crystal exhibited a strong absorption in ultraviolet region with the sharp absorption edge located at 340 nm and a significant blue fluorescent emission band at 442 nm. Ammonium 5-sulfosalicylic acid monohydrate (NH4 · C7H5O6S · H2O, ASSA) was synthesized and optical grade crystal with dimensions of 45 mm × 20 mm × 18 mm was obtained from aqueous solution by the cooling solution method. The crystal structure was confirmed by X The crystal belongs to monoclinic space group P21 / c with a = 11.884 (9), b = 7.306 (5), c = 12.152 (9) Final, β = 104.851 (13) °, V = 1019.8 (13) 3, Z = 4, Dc = 1.649 g / cm3, μ = 0.340 mm-1, F w R = 0.0866 for 7494 observed reflections (I> 2δ (I)). Elemental analysis, IR and 1H-NMR spectrum were used to characterize the compound. Thermal analysis showed that one coordination water molecule was contained and dehydration temperature of ASSA crystal was Optical transmission and fluorescence spectrum revealed that the ASSA crystal shows a strong absorption in ultraviolet region with the sharp absorption edge located at 340 nm and a significant blue fluorescent emission band at 442 nm.