The property of electrowetting on dielectric (EWOD) on the core-surface of variable-focus liquid lens with specific “conductive metal/insulation film/hydrophobic” material is one of the important research topics in optofluidics. Contact angle versus applied voltage (DC and AC) curve of conductive liquid droplets is obtained by experiment. Experimental results show that, to achieve the same effect as that obtained with DC power, what should be considered is the instantaneous maximum rather than the effective value (root-mean-square) when using low-frequency AC voltage. The variable-focus experiment of the variable-focus lens under the applied 50 Hz AC voltage is performed. A curve between the focal length of the variable-focus lens and the applied voltage is given. The experiment result agrees very well with the above analysis.