This study intends to clarify the forming characteristics of third liquid phase in phase transfer catalytic system in the presence of n-butanol and potassium hydroxide when tetrabutylammonium bromide, polyethylene glycol and their mixture serve as phase transfer catalyst, respectively. At 323 K, the three catalytic systems were applied to yield benzyl-n-butyl ether from benzyl chloride and n-butanol, and they performed distinct reaction activity. Among them, a combination of two kinds of catalyst results in a synergetic effect in reaction activity.