Photoinduced anisotropy of non-linear optical properties of Langmuir-Blodgett films of 4-nitro-4’-octadecilazobenzene has been studied for the first time by means of second harmonic generation. It was shown that the anisotropy of second order susceptibility of the films could be controlled by illuminating them by polarized visible CW radiation. The primary non-linear susceptibility corresponded to the direction perpendicular to the polarization vector of the CW radiation. These transformations of the films were reversible and could be repeated many times. Possible mechanisms of such a reconstruction of the films are discussed.