The principle of infrared thermography is presented briefly. And delamination defects of honeycomb aluminum composites were inspected by infrared thermography technique. Testing result showed that infrared thermography was a rapid, effective nondestructive evaluation method for delamination defects of composite materials. The optimal testing time for different defects was different. And the testing speed was higher than two screens per minute for all delamination defects of honeycomb aluminum composites. Rapid automatic heating modes, automatic synchronous scanning of heating source and infrared detector, and intelligentized defect identification system will be the important developing aspects of infrared thermography testing technique.