In order to expand the imaging depth of terahertz (THz) computed tomography (CT) system, 0.1 THz ultra long non diffractive beam was applied to continuous THz CT. A new type of faceted axicon was used to generate meter length non diffractive beam. A THz CT system for large-scale objects was built by using this non diffractive beam. With the support of the system, large-scale samples were scanned, and the projection data of the samples were obtained and reconstructed. The results show that, this new THz CT system can perform 3-D imaging of large-size samples with a diameter of 600 mm. And the internal 3-D structure of the object is obtained. This result provides an example for THz CT system for large-scale objects, and is helpful to expand the application scenarios of THz CT system.