The invention belongs to the wireless communication technology field and provides a millimeter-wave-terahertz-wave impedance tuner based on photonic crystal waveguide to realize the transmission coupling of a millimeter-wave-terahertz-wave system. The impedance tuner consists of a photonic crystal waveguide and an adjusting metal column. The photonic crystal waveguide consists of two metal plates and a plurality of fixed metal columns connected between the two metal plates. The photonic crystal waveguide is reserved by a defect structure along the middle line. The fixed metal columns are distributed symmetrically at two sides of the defect structure. The metal plates are further provided with a plurality of through holes symmetrically along the two sides of the defect structure. The adjusting metal column penetrates via the through holes the tube crystal waveguide and is in flexible connection with the metal plates. At the same time, the adjusting metal column and the fixed metal columns form together an array distribution. According to the invention, via the adjusting metal column, it is possible that metal columns in different numbers and array manners can be arranged in the tuner to form a plurality of impedance couplings. In addition, the tuner of the invention is low in cost and can be applied more widely.