Based on the optical characteristics of lead lanthanum zirconate titanate (PLZT) electro-optic ceramic, an optical phased-array beam deflector with up-down electrode structure′s transverse electro-optic effect was proposed. The electro-optic deflection characteristic and mechanism of the deflector were analyzed theoretically. And the phase modulation and electro-induced loss characteristics were measured experimentally. A systematic experiment of related optical phase-array devices and measuring system was also designed to verify the theoretical results. The results show that the beam obtains a relative large angle deflection by using different applied voltages.