The infrared detection range is an important indicator of the Infrared Searching and Tracking (IRST) system.How to quickly and accurately measure the infrared detection range has become a key part of IRST development.This paper analyzes the advantages and disadvantages of the current measuring method in the flight test,and proposes a new method to test the infrared detection range.This method uses the principle of contraction detection to introduce the real atmospheric path and real infrared scenes.The measurement of the infrared detection range is realized by accurately controlling the energy from a simulated radiating source.In view of the complicated and variable atmospheric transmittance near the ground,the correction factor of atmospheric transmittance is introduced to calibrate the atmospheric transmittance near the ground.Tests for two IRST systems of Type A and Type B were carried out.The maximum error between the measured infrared detection range and the flight test data was 12%.Compared with flight tests,this method greatly shortens the development cycle and reduces the development costs.