Experiments demonstrate that large varieties of animals have the ability to sense the magnetic field. Especially, some birds can use the geomagnetic field for navigation. According to the avian magnetoreception mechanisms, birds can build magnetic map for orientation and navigation by sensing the intensity and incline of geomagnetic field. However, researches on the magnetoreceptor of birds are still at the stage of discovery and identification, and it is necessary to study the iron-mineral-based structures to know whether they have the physical and magnetic properties to act as magnetoreceptor in living system. In this paper, the maghemite platelet chains in the iron-mineral-based magnetoreceptor have been studied with three-dimensional simulation based on the theories of micromagnetics. The reaction of the maghemite platelet chains with geomagnetic field has been investigated. Result indicates that the maghemite platelet chains with vortex domain can response to the change of the orientation of geomagnetic field.