To estimate the disbond defects of the carbon fiber composite materials with honeycomb sandwich structure applied in the aerospace, active infrared thermographic NDT (non-destructive testing) is researched. The specimen with known disbond defects is detected by an active infrared thermography system. The specimen is stimulated by a pulse heating source. Based on the thermal wave propagation theory, the surface temperature of the specimen contained defects will differ from the surrounding sound area because of their different thermal-physical properties. The surface temperature is monitored using infrared camera and analyzed by a computer in the time domain. The experiment results show that the active infrared thermographic NDT is rapid, effective and intuitive for detecting the disbond defects in composite materials with honeycomb sandwich structure.