Abstract: A optimum design scheme for 3 dimensions magneto optical card (3DMO card)storage system is presented. The 3DMO card possesses the features of large capacity, erasability and portability. By the use of the fiber optical head, the average access time of the storage system is decreased effectively. Based on the Borland C++, a optical expert system software is set up to simulate and analyze the pick-up signals. The technique is also suitable for the optical head design and simulation analysis of magneto-optical disk and other optical disk storage system.