The stilbene was synthesized via Wittig-Horner reaction in liquid-liquid phase-transfer catalysis (LL-PTC) system in which the NaOH aqueous solution and nonpolar solvent were used as the aqueous phase and the organic solvent, respectively. The effect of various catalysts, the amount of catalyst, the concentration of NaOH, the temperature and the various solvents were investigated. The activity of various aldehydes for Wittig-Horner reaction in LL-PTC system was also investigated. The optimum reaction condition was ascertained as follows: Tetraoctyl Ammonium Bromide（TOAB） as phase transfer catalysis, n(TOAB): n(Phosphonate)=1:10, 50% NaOH aqueous solution, at 45℃ and toluene as solvent. The yield was more than 96% under optimum reaction conditions. Wittig-Horner reaction showed high isolated yield and geometric selectivity (E-isomer) for various aldehydes in LL-PTC system.