The invention discloses a multi-dimensional multiplexing photonic terahertz communication system, which comprises an optical frequency comb generation module, a wavelength division multiplexing module, a signal modulation module, an optical branching module, a space division multiplexing fan-in module, a multiple Core fiber, space division multiplexing fan-out module, terahertz signal transmitting module, terahertz prism, terahertz signal receiving and demodulating module. The invention adopts an optical frequency comb generation module to generate an optical frequency comb with wide band and flat power distribution, and simultaneously transmits multiple optical signals through a space division multiplexing fan-in and fan-out module and a multi-core optical fiber. The invention combines multiple multiplexing technologies with the photonic terahertz wireless communication system. The system can adjust the number of carriers through the wavelength division multiplexing module, and adjust the number of branches through the space division multiplexing module, which can realize Tbit / s level The data transmission rate is high, the system capacity can be flexibly configured, the structure is simple, and the spectrum efficiency is high.