Since terahertz waves can penetrate non-metallic and non-polar materials, terahertz technology can make up for the shortcomings of laser technology and realize perspective ranging of the inside of the target. Terahertz perspective ranging technology based on chirp continuous wave is proposed, which realizes the non-contact measurement of the thickness and dielectric constant of multilayer dielectric materials, further expands the application range of terahertz chirp continuous wave, and provides a new way for the measurement of the dielectric constant of materials. Taking three common materials as the detection target, method is verified by using terahertz linear frequency modulated continuous waves in four frequency bands: 0. 11~ 0. 17 THz, 0. 17~ 0. 22 THz, 0. 22~ 0. 33 THz, and 0. 33~ 0. 50 THz, and it is proved that the measurement accuracy increases with the increase of the signal bandwidth, with errors below one percent. In addition, taking the ceramic material used to make radomes as the inspection target, applying the principle of terahertz perspective ranging and using the two-dimensional scanning frame to obtain all the information of this sample, perspective imaging and positioning of internal defects are realized.