Two methods of NETD-testing for the thermal infrared imager are briefly summarized in the paper.In need of NETD measurement in engineering,the SiTF method with higher accuracy but longer measuring time is adopted.Through the effort of optimizing the measurement steps and improving the image measurement algorithm,the measuring time is significantly reduced.Two measurements have been taken at different ambient temperatures,and the measurement results are stable and repeatable.The improved SiTF method provides an effective means for NETD engineering measurement.