Composite thin films of PbTiO3 nanocrystals and PEK-c polymer for applications in nonlinear optical devices were prepared by spin coating. The size of PbTiO3 nanocrystals was estimated to be 30-40 nm. The microstructure of PbTiO3/PEK-c composite polymer film before and after poling was analyzed by X-ray diffraction, which show that this film is c axis-orientated. The poled composite film displayed the refractive index anisotropy. In this sample the TE- and TM-indices differences are found to be 0.02945 for 633 nm and 0.03915 for 414 nm. The electro-optic coefficient gamma(33) of poled composite film was measured to be 12.89 pm V-1 at 633 nm by the transmission technique. The dielectric constant epsilon of it at 100 KHz under room temperature was determined to be 7.32. The figure of merit F-2 was estimated to be 492. In addition, a relaxation process was observed in the time range of 28 days and the relaxation time constant was calculated to be 2393 min. (C) 2004 Kluwer Academic Publishers.