We propose a new nonlinear optical material, a polymeric nanocomposite based on DAST submicron crystals (trans-4'-(dimethylamino)-N-methyl-4-stilbazolium tosylate). The method and the preparation conditions for films based on a mixture of polymer solutions and a DAST powder are studied. Polymer matrices of various types, solvent ratio for the pair DAST/polymer, and electrical poling conditions are investigated. Absorption and luminescence spectra and the second harmonic generation have confirmed the creation of red-form DAST nanocrystals in polymer films. The figure of merit for a resulting polymer film is approximately 400times higher than that for LiNbO3 at a wavelength of 1.32 microns.