A coupling model of imaging fiber and photo-detector array devices was established, and its coupling characteristic was studied via simulating method, which introduces different variable factors to represent the irregular arrange of imaging fiber. Based on 9×9 μm photosensitive cell, the influence to resolution was analyzed as fiber′s structure factors changing. A reasonable economic matching structure was obtained when fiber diameter was about one third size of the cell, that showed the optimal designing problem must be considered in the system design. Results of the computer emulation also explained the existence of the stripe and the formed reason of partial background structure in imaging fiber digital system, and the relevant method of numerical analysis was given.