Abstract: Since MTF measurement is important for evaluating the imaging quality of low-light-level image intensifier, the imaging plane position in the measurement system is adjusted to obtain accurate MTF measurement results. The optical imaging feature of LLL image intensifier MTF measurement system was analyzed, and the aberration of the optical system was discussed. The ideal setting of the imaging plane in LLL image intensifier MTF measurement was implemented by the method of the average middle value. By comparing the result with the known value of the image intensifier, this method is proved to be accurate.