An electrowetting-based double-liquid lens was developed to realize the small volume and automatic focusing without mechanical components for the focus-variation lens. The electrowetting-based double-liquid lens was designed and fabricated based on the dielectric wetting principle. Then, the focal length of liquid lens for different voltages was measured by a CCD image measurement system and it was compared with the theoretical value calculated by Gauss optical theory. Finally, COMSOL was employed to analyze the curvature radius of the double liquid interface at different voltages and to discuss the effect of dynamic viscosity on the response time and stability of the liquid lens. The results indicate that the double liquid interface bends to the conductive salt solution initially and then changes into a plane and finally bends to the insulating oil when the applied voltage is increased. Accordingly, the liquid lens changes from a concave lens to a convex lens, and the critical voltage is 50 V. However, the focal length of the liquid lens does not decrease any more when the applied voltage increases to 65 V. The whole focal length of the lens ranges from -∞ to -22.83 mm and from 33.47 mm to +∞, and it is adjusted continuously in a wider range. Moreover, when the dynamics viscosity of insulating oil is 0.03, the response time is 0.015 s and the corresponding performance of the device is optimal.