The invention provides a terahertz frequency mixing antenna and a quasi-optical frequency mixing module. The terahertz frequency mixing antenna comprises a first schottky diode, a second schottky diode, a planar antenna and a blocking condenser, wherein a negative pole of the first schottky diode is connected with a positive pole of the second schottky diode through the blocking condenser, and a positive pole of the first schottky diode is connected with a negative pole of the second schottky diode directly or through a resistance. The schottky diodes are arranged on radio frequency feed ports of the planar antenna, a radio frequency signal and a local oscillating signal are fed in a space coupling mode through the planar antenna, and an intermediate frequency signal is output after the frequency mixing of the schottky diodes and is output in a guided current mode from the outermost side of the planar antenna. The quasi-optical frequency mixing module comprises the terahertz frequency mixing antenna, a bias and intermediate frequency circuit and a planar transmission line. The terahertz frequency mixing antenna and the quasi-optical frequency mixing module are capable of being operated in a sub-harmonic frequency mixing mode or a fundamental wave frequency mixing mode, and being connected with a standard circuit port easily. Due to the fact that direct current bias is loaded on the frequency mixing antenna, requirements of local oscillating power is reduced.