Big-bore and flexible waveguides are fabricated for Terahertz wave transmission based on the structure of dielectric-coated metallic hollow waveguides.The liquid-phase coating technique for the dielectric film innercoating is modified and improved for the large-bore waveguides. The dielectric film thickness and the loss spectrum are the oretically and experimentally discussed. The experimental system is established to evaluate the transmission loss, additional bending attenuation, and output beam profile of the Terahertz (THz) waveguides at the frequency of 2.5 THz. According to the measured results, the transmission loss and additional bending attenuation are both decreased as the dielectric film thickness increases in the THz waveguides, while the energy distribution of beam profiles tends to focus on lower transmission modes.