Since the current information storage has low capacity and rate, 3d information storage method arises, with the unity of array laser, wavelength division multiplexing technology and multi-layer coating. This method mainly uses the optical fiber coupling lens to pull the focus of flare closer automatically, so that to read and write huge amounts of information. It will play an important role to reduce the three-dimensional storage seeking time. This article analyzes the principle of storage system and the theory of scalar diffraction of cd-rom system, and explores on the simulation results.