Abstract: In order to accurately evaluate the performance of an infrared thermal imager, it is necessary to test its modulation transfer function (MTF). In this paper, a CEDIT ⅡA thermal imaging system is measured and analyzed by the equipment with dual blackbody and reflective target system. The new testing method utilizes the theory of edge target test. The edge is differentiated to obtain the line spread function and Fouriertransformed to get the MTF. It is discovered that the primary factors which affect MTF test are the signal intensity for the testing system incidence, impulse noise suppression and acquisition filtering, etc. The equipment can keep even and steady radiation, and is not affected by ambient temperature, so the accuracy and reliability of measurement can be improved.