The spin of the electron has attracted renewed interest recently, because it promises a wide variety of new devices that combine logic, storage and sensor applications. But in the real world, numeric kinds of defects are always forming and existing while device fabrication processing, and affect the operating function of device away from its original design purpose more or less. Thus, the thesis is structured to get a series study of defect shapes, sizes, locations, and quantities influence of magnetization reversal process, based on magnetic thin film structure, and compared to basic shapes device performance for magnetic device design and fabrication defect control reference. Moreover, a prediction of defect influence of advanced technology nodes device is also given for next generation, or higher density magnetic device related reference.