Terahertz waves, electromagnetic waves possessing frequencies that fall within the range of 0.1 THz to 10 THz and wavelengths that span between 0.03 mm to 3 mm, have found their utility in various applications. It is, therefore, self-evident that the significance and imperative nature of deploying terahertz technology for non-destructive testing (NDT) cannot be overlooked. This article aims to acquaint the reader with a terahertz-based NDT system that comprises two parts, namely the hardware system and the software system, and explicate the operation principle of the system. Having successfully built the terahertz NDT system, diverse samples were subjected to testing. The results of these experiments reveal the suitability of the system for the inspection of different materials. In addition, surface imaging of composite structures was also performed, demonstrating the efficiency and precision of the terahertz NDT system in NDT. Consequently, the system presents a viable solution for the application of terahertz technology in the domain of NDT.