In the present work we studied the fabrication of ferroelectric film as PLZT by the sol-gel technique, and the birefringence optical property induced by the external voltage is measured by the electro-optic modulated heterodyne interferometer. The seeding layer as PT is deposited on the ITO glass substrate before the deposition of PLZT film. After the deposition of PLZT film, a conducting layer as SnO 2 is then coated on the top of PLZT. Experimental results show that there exists birefringence on this ferroelectric film we made by sol-gel method.