This paper presents a novel miniature system for measuring modulation transfer function (MTF) of CCD. This system consists of a miniature interferometer which can generate frequencies-variable sine grating patterns, data collection and transfer subsystem, software and hardware for data processing. The measured results show that the spatial frequencies of grating patterns generated by the interferometer can be continuously changed ranging from 0.2 to 80 line pair/mm with an error lower than 1 %. The modulation contrast of patterns is close to one. We have used the sine grating patterns generated by the interferometer as targets to measure the MTF of CCD array. The results are satisfactory.