Bi3.25La0.75Ti3O12 (BLT) thin film was prepared Oil quartz substrates using chemical solution deposition. The sign and magnitude of both real and imaginary pails of third-order nonlinear susceptibility chi((3)) of the BLT thin film have been determined by the Z-scan technique performed at 800 run with a femtosecond laser. The nonlinear refractive index coefficient gamma and the nonlinear absorption coefficient beta of the BLT thin film are - 1.915 x 10(-12) cm(2)/W and - 6.764 x 10(-8) m/W, respectively, the real part and imaginary part of the third-order nonlinear susceptibility chi((3)) of the BLT thin film are -5.81 X 10(-18) m(2)/V-2 and - 1.31 x 10-18 m(2)/V-2, respectively. Both the real and the imaginary parts of the third-order nonlinear susceptibility chi((3)) contribute to the nonlinearity of the film. These experimental results show that BLT thin film is a promising material for applications in nonlinear optical devices. (c) 2005 Elsevier B.V. All rights reserved.