Stainless steel-doped SrTiO3 thin films were fabricated by laser molecular beam epitaxy (L-MBE). Nonlinear optical property of the thin film was measured by the single beam Z-scan technique at the wavelength of 532 nm. Two two-phonon absorption coefficient and nonlinear refractive index were determined to be 9.37×10^(-7) m/W and 1.55×10^(-6) esu, respectively. The merit figure T was calculated to be 1.8, satisfying condition T < 2 for an optical switch. The thin film has a very promising prospect for the applications in optical device.