By introducing the contact-line static friction, a mechanical model for the contact line in a double-liquid variable-focus lens is established, which is a liquid-liquid-solid three phase system. The mechanical analysis on the contact line of the liquid-liquid-solid three phase system with non-ideal state is done again. On this basis, the Young′s equation is modified, and a reasonable explanation is given for the phenomenon of variable-focus hysteresis. The variable-focus experiment of the double-liquid variable-focus lens with dielectric layer thickness of 2 μm under the applied voltages is performed. A hysteresis curve between the focal length of the double-liquid variable-focus lens and the applied voltage is given. The experimental result agrees very well with the theoretical analysis.