Abstract: The liquid stub tuner is a new style impedance matching system used on the ion cyclotron resonance heating system in order to supersede the conventional piston stub tuner. Based on the research of the working theory of the liquid stub tuner, the oil loop system of the liquid stub tuner was designed, and computer and programmable logic controller were adopted to control the system. The method of calculating the height of each branch of the liquid stub tuner was studied, and calculating formulas were put forward and confirmed by the data of the experiment. The system has been employed for the EAST experiment for two times and is proved that it meets the requirement of the design.