Hydrate equilibrium conditions for tetra-n-butyl ammonium bromide (TBAB) aqueous solutions were experimentally studied and reported in the mole fraction from 0.003 to 0.047 and the temperature range of (276.35 to 285.65) K at atmospheric pressure. The phase change temperature of TBAB hydrate increases with the increase of the concentration of TBAB aqueous solution when the mole fraction of TBAB aqueous solution is less than 0.044.