Modulation transfer function is often used as a standard performance evaluation for optical components and imaging systems. The conventional test method for discrete optical element is the scanning knife –edge method. Because of the mosaic array architecture for taper and CCD, the integrated devices for CCD coupled with taper violate the isoplanatic conditions. The measured magnitudes of MTF vary with the position between edge and the array. In this paper, square-wave target MTF measurement was put forward. Square-wave targets with different spatial frequency were imaged by the integrated device, then transmit to the computer, the gray-scale value for the image of square-wave targets with certain spatial frequency could be got by the process program of image, so the CTF of the square-wave targets can be available, finally the MTF of the integrated device should got by the relationship between the CTF and MTF. The method avoids the influence of non-isoplanantic result from the dispersancy position between the ......