A tunable-focus liquid lens using dielectrophoretic effect is demonstrated. When a voltage is applied to a dielectric liquid droplet, the generated electric field inside the droplet is inhomogeneous. As a result, the liquid bears a dielectric force and its surface profile can be reshaped which causes the focal length to change. Adaptive lenses with different apertures are fabricated and their performances evaluated. In comparison to the patterned-electrode liquid lenses, our lens uses continuous electrode which is much simpler for fabrication.