In order to elucidate the photoinduced surface relief (PSR) phenomenon on azobenzene polymer film, the formulation of the PSR formation process is established analytically from Navier-Stokes equation on the basis of our viscous fluid model. The experimental data obtained by the systematic studies for two-beam coupling and one-dimensional (1D) Gaussian beam irradiation are reproduced very well by the model calculation. The good coincidence assures the feasibility of our theoretical model. Furthermore, an example for applying this phenomenon to 2D micro-image recording and/or high-density optical data storage is presented.