The existence of internal defects of aviation composites is a serious threat to air safety. In this paper, a novel infrared thermal imaging technique with laser as a heat source was applied to detect the internal defects in the carbon fiber reinforced plastics(CFRP) used in aviation field. With the advantages of remote feature and high-power density of laser, the positioning detection for the internal delamination defects of CFRP could be realized precisely. Multiple differential detection was carried out for the defect specimen as same as the reference specimen by using laser infrared thermal imaging technology. At the same time, according to the spatial position relationship between the specimen and the thermal imager, the max temperature difference in thermographs would be selected to calculate the diameter of the internal delaminate defect. The result shows that the laser infrared thermal imaging technology can effectively detect the internal delamination defects of CFRP. Especially, the differential laser infrared thermal imaging technology used for the first time can effectively eliminate the influence of the uneven laser energy distribution and make the defect image much clearer.