Crosstalk will lower down the modulation of the output signal of focal plane arrays (FPA), and then degrade the system′s overall modulation transfer function (MTF). With the development of photoelectric devices, using MTF to evaluate the performances of photoelectric devices is becoming more and more popular. Seen from the trend in civil imaging field, MTF will gradually replace typical parameters such as crosstalk and extreme resolution in evaluation of photoelectric devices. And this makes it a dilemma to decide whether to build a dedicated equipment for crosstalk measurement or not. Considering the relation between crosstalk and MTF, their correlation is analyzed qualitatively, starting from the definition and typical measurement method of crosstalk. It is pointed out that the difference between system′s overall MTF with and without crosstalk maximizes at the Nyquist frequency. Based on this, a new method of calculating percentage crosstalk from measured MTF curves of infrared FPAs is got.