Abstract: As an optical component for transferring image, fiber-optic image inverter has been extensively used in low-light-level image intensifier. The modulation transfer function (MTF) test system, on which slit is used, can be used to test the fiber-optic inverter-s MTF. But there is too much artificial participation during MTF testing, and the repeatability of inverter-s MTF is generally bad. Data sampling, integrating time and eyestrain which affected the repeatability of inverters MTF were respectively analyzed, the solution related to data sampling and integrating time was given, and the weighted correction method for eyestrain was presented. According to the six fiber-optic inverter-s MTF testing results and the comparison between direct correction and weighted correction of them, it is shown that the weighted correction solves the repeatability of inverter-s MTF well, and the maximum deviation for repeatability is less than 7%.