An experimental demonstration of the ultra-large-capacity terahertz (THz)-wave signal transmission over a 20-km wired and 54-m wireless distance in an 80-channel wavelength division multiplexing (WDM) system is successfully realized for the first time, to the best of our knowledge. Based on optical asymmetric single-sideband (ASSB) modulation and advanced digital signal processing (DSP) algorithms, we achieve a record line rate of 6.4 Tbit/s (net rate of 5.12 Tbit/s) in a THz-over-fiber communication system. This experimental demonstration can provide an effective solution for ultra-large-capacity THz-over-fiber communication in future 6G networks.