Aiming at the probem of lack of identifying criterion research for unitary infrared detection system of terminal sensitive projectile,an infrared detection identifying criterion based on the detection rate of infrared sensors is proposed. The relation between the product of the sensor’s detection rate and the target’s radiation power in the detected field of view and the signal-to-noise ratio of the detected signal is derived. It is used as the judgment basis for identifying the target. Simulation result shows that a cluster target can be detected and identified under the condition of the detection rate reaches a certain value and there is a temperature difference of more than 20 ℃ between the goal and the background,which can truly reflect the ability of the sensor’s detection and identification for armored target. The simulation results of using the criterion consistent with the actual test. It has a certain guiding significance for the infrared detection research of terminal sensitive projectile in the future.