In order to improve the technique of making microstructure on azobenzene polymer film, a new experimental method is presented, based on photoinduced isomerization and photoinduced birefringence of an amorphous copolymer containing azobenzene groups. Two-dimensional square microstructure is written on the azobenzene functional polymers film by two laser beams in a step-by-step procedure, so the pattern can be controlled in a convenient way. A new theory of photoinduced isomerization and re-orientation field is put forward. When azobenzene polymer film is irradiated by two beams and the polarization of these two beams are perpendicular, photoinduced isomerization and re-orientation field will occur and the interference can also take place. And the interference induces the formation of the grating on the surface of azobenzene polymer film. The results of the experiment and computer simulation are compared.