As an image-spectrum merging technology, hyperspectral imaging has been used in battlefield reconnaissance rapidly．According to the definition of MTF based on contrast, the theoretical model of the MTF of line-array CCD was presented. The effect of the relative position of line-array CCD and input signal on MTF was analyzed. The results indicate that at the frequency-division of Nyquist frequency, the relative position has a strong effect on the MTF, which becomes much stronger with frequency increase, while at other frequency, the effect of the relative position on MTF depends on the percent error ｜ζ｜, e.g. the bigger the value of ｜ζ｜, the weaker the effect of the relative position on MTF. In the frequency range of ｜ζ｜>0.1%, the effect of the relative position on MTF can be ignored. The above conclusions have directive significance in the design of MTF measure system of hyperspectral imager.