The structure of the magnetic mirror array device is designed. The modulation transfer function (MTF) of this device is calculated as well as that of magnetic mirror array image intensifier. The limiting resolutions of 117 lp/mm and 121 lp/mm of the magnetic mirror array device, by means of the analysis of MTF curves with the actual parameters, are obtained at X and Y directions in which the Nyquist frequencys are 0.55 and 0.59 respectively; while the limiting resolutions of magnetic mirror array image intensifier based on this device are 87 lp/mm and 89 lp/mm, and the corresponding Nyquist frequencys are 0.49 and 0.52 respectively. The results show that the difference between two curves at X and Y directions can be reduced to ensure better image quality. The calculation of this research provides an important theoretical basis for further research on the magnetic mirror array image intensifier.