With the definition of the contrast transfer function (CTF), CTF expression of line !array fiber !optic image bundles is established, the influence of phase matching between input signal and line ! array fiber !optic image bundles on the contrast transfer function is carried out by digital analysis. The results show that alignment between pixels of image bundle and input pattern has cyclic variation on measure result of the CTF. When frequency of the input pattern is less than Nyquist frequency, the CTF value decreases with increase of the frequency.