In this paper, theoretical analysis of the cylindrical double-liquid lens model with single-layer dielectric film, tells us that the thickness and uniformity of the dielectric film have great influence on the performance of variable-focus double liquid lens. The relation curve between focal length of liquid lens and driving voltage is drawn. On this basis, parylene is chosen as the dielectric film of low voltage variable-focus double liquid lens to reduce the driving voltage. The parylene film inside the cylindrical chamber with suitable thickness is coated by vacuum evaporation, and the surface appearance and the thickness of the film are also measured. In the experiment, the conducting liquid of potassium chloride and insulating liquid of silicone oil are chosen, with centrifugal degasification processing before used. At last, a sample of liquid lens is produced. The sample has excellent property with focal range ±20 V under the maximum driving voltage 30 V. The friction term is introduced into Yong′s equation and a reasonable explanation is given for the phnomenon of variable-focus hysteresis.