This paper have introduced the application of the electromagnetic wave CT method in highway engineering. And the contrast reaserch about the electromagneitc wave absorption cofficient CT 2D and 3D image have been made. The results show that the 2D image can reflect the undergound structure between two drillings, and 3D image contains more information, such as the electromagneric wave absorption coefficient section of different depths. The 3D image can reproduce the structures of underground medium and provide more detailed information for engineering geological exploration.