The orientation of the azo dye molecules in polymer film induced by all optical poling is investigated and modeled. According to this model, when both writing beams with frequencies of ω and 2ω are linearly polarized with polarization direction parallel to each other, the majority of molecules in the films axially align in the direction perpendicular to the polarization of the writing beams, while the minority of molecules polarly align in the parallel direction, but only the latter contributes to the macroscopic second order nonlinearity in the polymer film. The model has been experimentally confirmed.