To control the light steering direction in three-dimensional space, a liquid prism array system based on electrowetting-on-dielectric (EWOD) is proposed. According to the geometrical optics and EWOD theory, the relationships among the beam steering angle, maximum beam steering angle, EWOD contact angle, interval between adjacent prisms, and liquid refractive index are analyzed and discussed. A theoretical model of an EWOD liquid prism array is constructed in COMSOL. Then, the evolution of the double liquid interface in the liquid prism unit is simulated under different voltages. The beam steering control characteristics of the liquid prism array are simulated. Results demonstrate that the EWOD based liquid prism array can realize continuous beam steering control in a certain range. By selecting a specific combination of liquids, the saturation contact angle can decrease to 45°, and consequently the range of beam steering angle for the liquid prism unit reaches 28° (from -14° to 14°). As the optical axis spacing r is set to 6 mm, the steering region of the liquid prism array system is in a conical region whose apex angle is 28°, and the corresponding vertex of the cone is located at Z=22.58 mm in the Z-axis.